Preparation method and application of temperature-regulated lignin-based porous carbon material
By preparing lignin-based porous carbon materials through temperature control, the problem of ineffective utilization of lignin was solved, the catalytic activity of CO2 cycloaddition reaction was improved, and the high-value conversion of lignin and resource recycling were achieved.
Patent Information
- Application Number
- CN202510720277.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-30
- Publication Date
- 2025-09-19
AI Technical Summary
In the existing technology, lignin is mainly burned as a low-value fuel and has not been effectively utilized. In addition, the preparation of traditional carbon materials relies on fossil energy, resulting in environmental pollution and waste of resources, and it is difficult to efficiently catalyze CO2 cycloaddition reactions.
Lignin-based porous carbon materials were prepared by temperature control method. Potassium citrate and sodium lignin sulfonate were used as precursors, combined with chemical activation method, to prepare porous carbon materials with different specific surface areas and pore structures for catalyzing CO2 cycloaddition reaction.
It achieves high-value conversion of lignin, improves the catalytic activity of CO2 cycloaddition reaction, increases the yield of cyclic carbonates, reduces reaction by-products, and realizes efficient utilization of biomass resources.
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Figure CN120662290A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of research and development of modified lignin carbon materials, and specifically relates to the preparation of a temperature-controlled lignin-based porous carbon material and its application in catalyzing CO2 cycloaddition reactions. Background Art
[0002] The use of fossil energy is inevitable in the process of industrial development. Traditional carbon materials mainly rely on fossil energy for synthesis, leading to environmental pollution and global warming. Lignin, as the most abundant renewable aromatic source on Earth, is a friendly biomass carbon source that can replace traditional chemical raw materials to prepare carbon materials, reducing dependence on fossil energy. Currently, 95% of industrial lignin is directly burned as a low-value fuel, and only 2% is used as a substitute for chemicals or materials. Therefore, upgrading lignin waste into alternative and high-value porous carbon catalysts for the catalytic conversion of CO2 is one of the promising and challenging issues. Summary of the Invention
[0003] Based on the above deficiencies in the prior art, the technical problem solved by the present invention is to provide a method for catalyzing CO2 cycloaddition reaction by temperature-regulated lignin-based carbon materials. The temperature-regulated lignin-based carbon materials are calcined at different temperatures to obtain porous carbon materials with different specific surface areas, thereby promoting the catalytic activity of the CO2 cycloaddition reaction, realizing high-value conversion of lignin and CO2, and achieving the purpose of effective recycling of carbon resources.
[0004] In order to solve the above technical problems, the present invention provides a method for preparing a temperature-controlled lignin-based porous carbon material, comprising the following steps: adding a saturated solution of potassium citrate dropwise to sodium lignin sulfonate, stirring and mixing, impregnating for 3 to 7 hours, and vacuum drying to obtain a lignin precursor; calcining the obtained lignin precursor to obtain a lignin carbon material; placing the lignin carbon material in a 1 to 4M hydrochloric acid solution for pickling for 2 to 6 hours, then washing with deionized water until neutral, and then drying; the dried lignin carbon material is ground into 100 to 300 meshes in a mortar to obtain a temperature-controlled lignin-based porous carbon material.
[0005] As a preferred embodiment of the above technical solution, the method for preparing the temperature-regulated lignin-based porous carbon material provided by the present invention further includes some or all of the following technical features:
[0006] As an improvement of the above technical solution, the mass ratio of the sodium lignin sulfonate to potassium citrate is 1:2-5; wherein, in the saturated potassium citrate solution, the ratio of potassium citrate to deionized water is in the range of 2-5g:1-3ml.
[0007] As an improvement of the above technical solution, the vacuum drying temperature is 40 to 80° C., and the drying time is 8 to 24 hours.
[0008] As an improvement of the above technical solution, the calcination conditions are heating at 300-1000° C. for 1-6 hours, and a heating rate of 1-5° C. / min.
[0009] As an improvement of the above technical solution, the drying condition is drying at a temperature range of 80 to 120° C. for 9 to 18 hours.
[0010] The present invention also provides a temperature-controlled lignin-based porous carbon material, which is prepared by any of the above methods, and has a pore size distribution mainly consisting of micropores and mesopores, and a specific surface area of 51 to 2024 m 2 .g -1 .
[0011] The present invention further provides a use of any of the temperature-regulated lignin-based porous carbon materials described above, wherein the temperature-regulated lignin-based porous carbon material is used as a catalyst to catalyze a CO2 cycloaddition reaction.
[0012] As a preferred embodiment of the above technical solution, the application of the temperature-regulated lignin-based porous carbon material provided by the present invention further includes some or all of the following technical features:
[0013] As an improvement of the above technical solution, the specific catalytic reaction steps are as follows: styrene oxide, catalyst, and co-catalyst KI are heated to react in a CO2 atmosphere. After the reaction is completed, it is cooled to room temperature, excess CO2 is discharged, solvent ethyl acetate is added to extract the product, and the supernatant is collected after centrifugation to collect the product.
[0014]
[0015] As an improvement of the above technical solution, the mass ratio of styrene oxide to catalyst is 80-20:1, the molar ratio of styrene oxide to KI is in the range of 5-30 mmol:0.1-2 mmol, the CO2 pressure is 0.5-2 MPa, the reaction temperature is 100-140°C, and the reaction time is 3-9 h.
[0016] As an improvement of the above technical solution, the amount of the solvent ethyl acetate added is 5 to 20 ml.
[0017] Sodium lignin sulfonate (SL) and potassium citrate extracted by the sulfate method are used as precursors through an impregnation method, and calcined to prepare a lignin-based porous carbon material with a high specific surface area. The developed pore structure and high specific surface area cooperate with the oxygen-containing functional groups hydroxyl and carboxyl to promote the catalytic reaction of CO2 and epoxy compounds. Experimental results show that the lignin porous carbon (SLAC) calcined at different temperatures has excellent catalytic activity for CO2 cycloaddition reaction, and the yield of cyclic carbonates can reach 94.7%. Compared with the 41.2% yield of cyclic carbonates synthesized without the addition of potassium citrate, the catalytic activity of the lignin porous carbon material (SLAC) is significantly improved. The present invention not only expands the value-added utilization of lignin, but also converts CO2 into high-value chemicals.
[0018] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:
[0019] (1) The present invention uses green and renewable lignin as the main body, prepares lignin-based porous carbon, designs efficient and stable biomass-based carbon material catalysts, and applies them to CO2 cycloaddition reactions, thereby providing a platform for the high-value conversion of biomass resources and CO2 into chemicals.
[0020] (2) The present invention uses a simple chemical activation method to achieve the purpose of retaining some functional groups in lignin-based porous carbon while increasing its specific surface area, and the synergistic effect achieves high reaction catalytic activity of CO2 cycloaddition.
[0021] (3) The reaction conditions of the present invention are mild, do not involve high temperature and high pressure, have few side reactions, and have little impact on reaction equipment and the environment.
[0022] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the following is a detailed description in conjunction with the preferred embodiments. BRIEF DESCRIPTION OF THE DRAWINGS
[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings of the embodiments are briefly introduced below.
[0024] Figure 1 This is a reaction principle diagram of the temperature-controlled lignin-based porous carbon material catalyzing the CO2 cycloaddition reaction of the present invention;
[0025] Figure 2 is the infrared spectra of lignin-based porous carbon materials calcined at different temperatures;
[0026] Figure 3 The effect of calcination at different temperatures on the morphology of lignin-based porous carbon materials. DETAILED DESCRIPTION
[0027] The specific embodiments of the present invention are described in detail below. As a part of this specification, the embodiments illustrate the principles of the present invention through examples. Other aspects, features and advantages of the present invention will become clear through the detailed description.
[0028] The present invention adopts chemical activation method to prepare a series of lignin-based porous carbon materials, and retains some hydroxyl and carboxyl active centers through calcination at different temperatures to promote the catalytic reaction performance of CO2 and epoxide in synergistic manner with high specific surface area.
[0029] Example 1: (1) Preparation of lignin porous carbon material (SLAC-400℃): Take an appropriate amount of potassium citrate and deionized water and fully dissolve them to obtain a saturated potassium citrate solution, add it dropwise to 1g of sodium lignin sulfonate, stir and mix, and soak for 5h. After being fully mixed, transfer it to a vacuum drying oven and dry it at a temperature of 60℃ for 12h; place the obtained lignin precursor in a tube furnace at 400℃ and calcine it at a heating rate of 3℃ / min for 2h; the calcined lignin carbon material is placed in a 2M hydrochloric acid solution for pickling for 3h and then washed with deionized water to neutrality (PH=7), and placed in a blast drying oven at 100℃ for drying for 12h; the dried lignin carbon material is ground into 250 mesh using a mortar to obtain a temperature-controlled lignin-based porous carbon material.
[0030] (2) Carbon dioxide cycloaddition reaction: A 25 ml autoclave was filled with styrene oxide (15 mmol) at a mass ratio of styrene oxide to catalyst of 36:1, a cocatalyst KI (0.1 mmol) and 1 MPa of CO2. The reaction temperature was set at 120°C for 6 h. After the reaction was completed, the mixture was cooled to room temperature in an ice bath and the excess CO2 was discharged (the tail gas was absorbed with ethyl acetate). 8 ml of ethyl acetate was added to the reaction solution to extract the product. After centrifugation, the supernatant was collected and quantitatively analyzed by gas chromatography (internal standard method) and flame ionization detector (FID). The yield of the product styrene carbonate (SC) was further calculated in combination with GC-MS.
[0031] Example 2: (1) Preparation of lignin porous carbon material (SLAC-500℃): Take an appropriate amount of potassium citrate and deionized water and fully dissolve them to obtain a saturated potassium citrate solution, add it dropwise to 1g of sodium lignin sulfonate while stirring, mix and soak for 5h, and after being fully mixed, transfer it to a vacuum drying oven and dry it at a temperature of 60℃ for 12h; place the obtained lignin precursor in a tube furnace at 500℃ and calcine it at a heating rate of 3℃ / min for 2h; the calcined lignin carbon material is placed in a 2M hydrochloric acid solution for pickling for 3h and then washed with deionized water until neutral (PH=7), and placed in a blast drying oven at 100℃ for drying for 12h; the dried lignin carbon material is ground into 250 mesh using a mortar to obtain a temperature-controlled lignin-based porous carbon material.
[0032] (2) (2) in Synchronous Example 1
[0033] Example 3: (1) Preparation of lignin porous carbon material (SLAC-600℃): Take an appropriate amount of potassium citrate and deionized water and fully dissolve them to obtain a saturated potassium citrate solution, add it dropwise to 1g of sodium lignin sulfonate while stirring, mix and soak for 5h, and after being fully mixed, transfer it to a vacuum drying oven and dry it at a temperature of 60℃ for 12h; place the obtained lignin precursor in a tube furnace at 600℃ and calcine it at a heating rate of 3℃ / min for 2h; the calcined lignin carbon material is placed in a 2M hydrochloric acid solution for pickling for 3h and then washed with deionized water until neutral (PH=7), and placed in a blast drying oven at 100℃ for drying for 12h; the dried lignin carbon material is ground into 250 mesh using a mortar to obtain a temperature-controlled lignin-based porous carbon material.
[0034] (2) (2) in Synchronous Example 1
[0035] Example 4: (1) Preparation of lignin porous carbon material (SLAC-800℃): Take an appropriate amount of potassium citrate and deionized water and fully dissolve them to obtain a saturated potassium citrate solution, add it dropwise to 1g of sodium lignin sulfonate, stir and mix, and soak for 5h. After being fully mixed, transfer it to a vacuum drying oven and dry it at a temperature of 60℃ for 12h; place the obtained lignin precursor in a tube furnace at 500℃ and calcine it at a heating rate of 3℃ / min for 2h; the calcined lignin carbon material is placed in a 2M hydrochloric acid solution for pickling for 3h and then washed with deionized water to neutrality (PH=7), and placed in a blast drying oven at 100℃ for drying for 12h; the dried lignin carbon material is ground into 250 mesh using a mortar to obtain a temperature-controlled lignin-based porous carbon material.
[0036] (2) (2) in Synchronous Example 1
[0037] Example 5 (Control): Carbon dioxide cycloaddition reaction: A 25ml autoclave was filled with styrene oxide (15 mmol) at a mass ratio of styrene oxide to catalyst (SL) of 36:1, a cocatalyst KI (0.1 mmol), and 1 MPa of CO2. The reaction was set at 120°C for 6 hours. After the reaction was completed, the reaction was cooled to room temperature in an ice bath and the excess CO2 was discharged (with ethyl acetate to absorb the tail gas). 8 ml of ethyl acetate was added to the reaction solution to extract the product. After centrifugation, the supernatant was collected and quantitatively analyzed by gas chromatography (internal standard method) and flame ionization detection (FID). The yield of the product, styrene carbonate (SC), was further calculated in combination with GC-MS.
[0038] The characterization of the lignin porous carbon material and the experimental data of the CO2 cycloaddition reaction in the example are as follows:
[0039] Figure 2.Infrared spectra of lignin porous carbon calcined at different temperatures, including SLAC-400 (400℃), SLAC-500 (500℃), SLAC-600 (600℃), SLAC-800 (800℃), sodium lignin sulfonate (SL); Attached Figure 2 The infrared spectra of lignin porous carbon calcined at different temperatures. The characteristic peaks of sodium lignin sulfonate are distributed as follows: 3442 cm -1 The strong peak at 2931cm is attributed to the stretching vibration of OH of hydroxyl and carboxyl groups. -1 The peaks near 1614cm correspond to CH stretching vibration. -1 、1407cm -1 The peaks near 1321cm are caused by the C=C vibration of the aromatic ring. -1 The absorption peak belongs to the bending vibration of OH of carboxyl group. 1137cm -1 、1043cm -1 、624cm -1 The peaks belong to the antisymmetric and symmetric stretching vibrations of the sulfonic acid group. Compared with the original sodium lignin sulfonate, the absorption peaks of the carbonized lignin porous carbon are reduced and weakened, which is due to the dehydration effect of potassium citrate and the decomposition of organic matter.
[0040] Figure 3 Effect of different temperatures on the morphology of porous carbon calcined with lignin, including (a) SLAC-400℃, (b) SLAC-500℃, (c) SLAC-600℃, (d) SLAC-800℃; Appendix Figure 3 The morphological characteristics of porous lignin carbon calcined at different temperatures are shown in the figure. The surface of the porous lignin carbon calcined at all temperatures is rough, with larger pores at 400°C. As the carbonization temperature increases, the porous structure increases, and the surface pore size distribution becomes tighter, resulting in a variety of pore sizes. PCLC calcined at 400°C exhibits a small number of macropores, which can promote CO2 mass transfer and make it suitable as a catalyst for the reaction.
[0041] Table 1. Hydroxyl and carboxyl content of lignin porous carbon materials by Bohem titration
[0042]
[0043] Table 2. Ratio of COOH / phenolic hydroxyl groups in lignin porous carbon materials
[0044]
[0045] Lignin itself contains rich functional groups, and the content of hydroxyl and carboxyl groups in the lignin of the present invention is quantitatively analyzed by Bohem titration. It can be observed from Table 1 that as the temperature increases, the phenolic hydroxyl content first decreases and then increases. As the temperature rises from SLAC-400℃ to 600℃, the phenolic hydroxyl skeleton decreases. The phenolic hydroxyl content of the catalyst at 400℃ is 0.4696mmol / g. The increase in phenolic hydroxyl content at 800℃ may be due to the increase in specific surface area, resulting in a more complete reaction between the reaction liquid and the phenolic hydroxyl group. According to the -COOH / phenolic hydroxyl ratio in Table 2, it can be seen that temperature changes can regulate the proportion of carboxyl groups in the lignin porous carbon material, among which the proportion of carboxyl groups at SLAC-800℃ is significantly improved.
[0046] Table 3. Pore size distribution of lignin porous carbon materials in Example
[0047]
[0048] As shown in Table 3, the surface area and pore volume of the original sodium lignin sulfonate are very small. With the increase of calcination temperature, the specific surface area increases and can reach a maximum of 2024m 2 .g -1 The average pore size distribution at SLAC-400℃ is mainly mesopores of 23.19nm, while the pore size distribution of catalysts at other temperatures is mainly micropores. The higher the temperature, the larger the pore volume of the lignin porous carbon material. Combined with the active sites provided by the hydroxyl and carboxyl groups, the catalytic effect is best when SLAC-400℃ is used as the catalyst.
[0049] Table 4. Catalytic activity of CO2 cycloaddition reaction catalyzed by lignin porous carbon materials in Example
[0050]
[0051] As shown in Table 4, the lignin porous carbon catalyst (SLAC) exhibited significant improvements in both yield and selectivity compared to the original sodium lignosulfonate (SL). This suggests that increasing the specific surface area by expanding the pores of lignin promotes catalytic activity in the CO2 cycloaddition reaction. Furthermore, the ring-opening rate is a crucial factor in catalytic activity in the CO2 cycloaddition reaction. The SLAC-400°C catalyst, which provides more hydroxyl and carboxyl active centers and a higher specific surface area, achieved a 94.7% yield of styrene carbonate (SC).
[0052] The raw materials listed in the present invention, as well as the upper and lower limits and interval values of the raw materials, and the upper and lower limits and interval values of the process parameters (such as temperature, time, etc.) can all realize the present invention, and the embodiments are not listed one by one here.
[0053] The above description is only a preferred embodiment of the present invention, which certainly cannot be used to limit the scope of rights of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and changes can be made without departing from the principles of the present invention. These improvements and changes are also considered to be within the scope of protection of the present invention.
Claims
1. A method for preparing a temperature-controlled lignin-based porous carbon material, characterized in that: The method comprises the following steps: adding a saturated potassium citrate solution dropwise to sodium lignin sulfonate, stirring and then mixing and impregnating for 3 to 7 hours, and vacuum drying to obtain a lignin precursor; calcining the obtained lignin precursor to obtain a lignin carbon material; placing the lignin carbon material in a 1 to 4M hydrochloric acid solution for pickling for 2 to 6 hours, then washing with deionized water until neutral, and then drying; and grinding the dried lignin carbon material into 100 to 300 meshes in a mortar to obtain a temperature-controlled lignin-based porous carbon material.
2. The method for preparing a temperature-controlled lignin-based porous carbon material according to claim 1, wherein: The mass ratio of the sodium lignin sulfonate to potassium citrate is 1:2-5; wherein, in the saturated potassium citrate solution, the ratio of potassium citrate to deionized water is in the range of 2-5 g:1-3 ml.
3. The method for preparing a temperature-controlled lignin-based porous carbon material according to claim 1, wherein: The vacuum drying temperature is 40 to 80° C., and the drying time is 8 to 24 hours.
4. The method for preparing a temperature-controlled lignin-based porous carbon material according to claim 1, wherein: The calcination conditions are as follows: heating at 300-1000° C. for 1-6 hours, and a heating rate of 1-5° C. / min.
5. The method for preparing a temperature-controlled lignin-based porous carbon material according to claim 1, wherein: The drying condition is drying at a temperature range of 80 to 120° C. for 9 to 18 hours.
6. A temperature-regulated lignin-based porous carbon material, characterized in that: The temperature-controlled lignin-based porous carbon material is prepared by the method according to any one of claims 1 to 5, and its pore size distribution is mainly micropores and mesopores, and the specific surface area is 51 to 2024 m 2 .g -1 .
7. A use of the temperature-controlled lignin-based porous carbon material according to any one of claims 1 to 6, characterized in that: The temperature-regulated lignin-based porous carbon material is used as a catalyst to catalyze CO2 cycloaddition reaction.
8. The use of the temperature-controlled lignin-based porous carbon material according to claim 7, wherein: The specific catalytic reaction steps are as follows: styrene oxide, catalyst, and co-catalyst KI are heated to react in a CO2 atmosphere. After the reaction is completed, the mixture is cooled to room temperature, excess CO2 is discharged, solvent ethyl acetate is added to extract the product, and the supernatant is collected after centrifugation.
9. The method for preparing a temperature-controlled lignin-based porous carbon material according to claim 8, wherein: The mass ratio of styrene oxide to catalyst is 80-20:1, the molar ratio of styrene oxide to KI is in the range of 5-30 mmol:0.1-2 mmol, the pressure of CO2 is 0.5-2 MPa, the reaction temperature is 100-140° C., and the reaction time is 3-9 h.
10. The method for preparing a temperature-controlled lignin-based porous carbon material according to claim 8, wherein: The amount of ethyl acetate added is 5 to 20 ml.