A lignin depolymerization catalyst, its preparation method and application
By introducing H4PMo11VO40 onto g-C3N4 to prepare a lignin depolymerization catalyst, combined with photocatalysis and a low eutectic solvent, the problem of low selectivity in lignin depolymerization was solved, achieving the production of monophenolic compounds with high selectivity and high yield, and providing a green and sustainable production method.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- BEIHUA UNIV
- Filing Date
- 2024-04-01
- Publication Date
- 2026-07-17
Smart Images
Figure CN118341458B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of lignin depolymerization treatment technology, and in particular to a lignin depolymerization catalyst, its preparation method and application. Background Technology
[0002] Lignin, as the most abundant natural phenolic polymer, is produced in enormous quantities annually. However, this resource is not effectively utilized. For example, the pulp and paper industry generates a large amount of lignin byproducts each year, most of which are burned for heat and electricity production, with only a very small amount used to produce other chemicals. This phenomenon results in a serious waste of lignin resources. Phenols, as important chemical raw materials, are mostly extracted from fossil fuels or synthesized through chemical methods. However, with the increasing depletion of fossil energy, the preparation of monophenolic compounds (such as syringic acid, vanillin, eugenol, and acetylsyleugenone) from lignin has attracted widespread attention from scholars in the industry. These compounds can replace petrochemical phenols in the synthesis of various phenolic resins and biomass-based wood adhesives. Furthermore, after separation and purification, aromatic aldehydes can be obtained for the manufacture of high-value-added chemical products such as fragrances, dyes, and pharmaceuticals. Therefore, depolymerizing lignin into monophenolic compounds, and thus realizing the high-value utilization of lignin resources, has significant scientific importance and potential socio-economic value.
[0003] Lignin catalytic depolymerization boasts advantages such as low reaction energy consumption, relatively mild conditions, and high conversion rates, making it considered one of the most promising methods for the high-value utilization of lignin. Chemical catalysts used for lignin depolymerization can generally be further classified into five different categories: acid catalysis, base catalysis, metal catalysis, ionic liquid-assisted catalysis, and supercritical fluid-assisted catalysis. Different catalysts can be combined simultaneously or applied to different stages of the depolymerization process to improve efficiency and produce the desired product. Due to lignin's low cost, high reserves, and unique aromatic structure, lignin depolymerization can prepare monophenolic compounds. However, currently obtained monophenolic compounds are all mixtures, and the amount of a single product depends on the source of the lignin and its separation process. Therefore, improving the selectivity of lignin depolymerization and producing a single product becomes particularly important.
[0004] In recent years, non-metallic two-dimensional (2D) carbon nitride (g-C3N4) materials have attracted attention due to their advantages such as convenient synthesis, high stability, suitable band structure (2.7 eV), and non-toxicity and pollution-free nature. g-C3N4 is an organic semiconductor polymer with sp atoms between C and N atoms. 2The hybridized triazine structure allows it to absorb visible light in the 440–460 nm range, making it widely applicable in photocatalytic water splitting for hydrogen production, pollutant degradation, CO2 reduction, and organic synthesis. However, g-C3N4 has a low specific surface area and a high photogenerated electron-hole recombination rate, necessitating structural modification to improve its photocatalytic performance, such as introducing defect structures, constructing heterojunctions, and doping with other atoms. However, research on its application in the catalytic depolymerization of lignin is scarce, and its application in the highly selective conversion of lignin into monophenolic compounds remains a significant challenge.
[0005] Therefore, how to disclose a lignin depolymerization catalyst, its preparation method and application, improve the selectivity of lignin depolymerization and increase the yield of single products is an urgent problem to be solved in this field. Summary of the Invention
[0006] In view of this, the present invention provides a lignin depolymerization catalyst, its preparation method and application, to solve the problems of existing lignin catalytic depolymerization methods where the products are all mixtures, the selectivity is low, and the amount of a single product depends on the source of lignin and its separation process.
[0007] To achieve the above objectives, the present invention adopts the following technical solution:
[0008] A method for preparing a lignin depolymerization catalyst includes the following steps:
[0009] The g-C3N4 dispersion was mixed with H4PMo 11 VO 40 The solutions were mixed and dried to obtain a lignin depolymerization catalyst.
[0010] Preferably, the method for preparing the g-C3N4 dispersion includes dispersing g-C3N4 in water;
[0011] The mass-to-volume ratio of g-C3N4 to water in the g-C3N4 dispersion is 0.5g:15-25mL.
[0012] Preferably, the H4PMo 11 VO 40 The solvent for the solution is ethanol and / or water;
[0013] The H4PMo 11 VO 40 H4PMo in solution 11 VO 40 The mass-to-volume ratio of the solvent to the total volume is 0.1–0.2 g: 6–8 mL.
[0014] Preferably, the g-C3N4 in the g-C3N4 dispersion contains g-C3N4 and H4PMo 11 VO40 H4PMo in solution 11 VO 40 The mass ratio is 100:15 to 45.
[0015] Preferably, the mixing is H4PMo 11 VO 40 The solution was added dropwise to the g-C3N4 dispersion;
[0016] The drop rate is 20-30 drops / min.
[0017] Another object of the present invention is to provide a lignin depolymerization catalyst prepared by the preparation method described above.
[0018] Another object of the present invention is to provide an application of a lignin depolymerization catalyst in the depolymerization of lignin, comprising the following steps:
[0019] Lignin, a lignin depolymerization catalyst, a eutectic solvent, and water were mixed and subjected to a depolymerization reaction under light irradiation to obtain 4-butyryl-2-methoxyphenol.
[0020] Preferably, the mass-to-volume ratio of lignin, lignin depolymerization catalyst, eutectic solvent and water is 0.08–0.12 g: 0.18–0.22 g: 18–22 mL: 0.8–1.2 mL.
[0021] Preferably, the eutectic solvent is a mixture of choline chloride and toluenesulfonic acid.
[0022] Preferably, the temperature of the depolymerization reaction is 70–100°C, and the time of the depolymerization reaction is 5–8 hours.
[0023] As can be seen from the above technical solution, compared with the prior art, the present invention has the following beneficial effects:
[0024] Using Keggin-structured polyoxometalates as catalysts can solve many technical problems in the conversion of lignin to 4-butyryl-2-methoxyphenol:
[0025] 1. H4PMo was introduced onto graphitic carbon nitride. 11 VO 40 of The addition of acid sites improves the acidity and recyclability of the catalyst. The yield and selectivity for the catalytic preparation of 4-butyryl-2-methoxyphenol are both higher than those achieved using H4PMo alone. 11 VO 40 The results were obtained using g-C3N4 as a catalyst. Meanwhile, H4PMo... 11 VO 40 The qualities possessed The synergistic effect of acidity, oxidizing properties, and the photocatalytic properties of g-C3N4 can better meet the requirements for the conversion of lignin to 4-butyryl-2-methoxyphenol.
[0026] 2. The catalyst disclosed in this invention exhibits high catalytic activity in the photocatalytic depolymerization of lignin to 4-butyryl-2-methoxyphenol, and shows high yield and selectivity of 4-butyryl-2-methoxyphenol during the conversion process.
[0027] 3. The catalyst disclosed in this invention is stable during the reaction process and is easy to recover and recycle. This catalyst is suitable for one-pot production of 4-butyryl-2-methoxyphenol in a DES (eutectic solvent) system. This method is green and environmentally friendly because its high selectivity and high yield can reduce the separation and purification costs of the target product, making it a green and sustainable new method for the conversion of lignin to 4-butyryl-2-methoxyphenol. Attached Figure Description
[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.
[0029] Figure 1 The image shows the GC-MS diagram of 4-butyryl-2-methoxyphenol prepared in Example 1. Detailed Implementation
[0030] This invention provides a method for preparing a lignin depolymerization catalyst, comprising the following steps:
[0031] The g-C3N4 dispersion was mixed with H4PMo 11 VO 40 The solutions were mixed and dried to obtain a lignin depolymerization catalyst.
[0032] In this invention, the preparation method of the g-C3N4 dispersion includes dispersing g-C3N4 in water.
[0033] In this invention, the mass-to-volume ratio of g-C3N4 to water in the g-C3N4 dispersion is 0.5g:15-25mL, preferably 0.5g:16-24mL, more preferably 0.5g:18-22mL, and even more preferably 0.5g:20mL.
[0034] In this invention, the particle size of the g-C3N4 is 10-15 μm, specifically 11 μm, 12 μm, 13 μm, or 14 μm.
[0035] In this invention, the H4PMo 11 VO 40 The solvent for the solution is ethanol and / or water.
[0036] In this invention, when the solvent is a mixture of ethanol and water, the volume ratio of ethanol to water is 1:0.8 to 1.2, preferably 1:0.9 to 1.1, and more preferably 1:1.
[0037] In this invention, the H4PMo 11 VO 40 H4PMo in solution 11 VO 40 The mass-to-volume ratio of the solvent to the content of the solvent is 0.1-0.2 g: 6-8 mL, preferably 0.12-0.18: 6.2-7.8, more preferably 0.14-0.16: 6.5-7.5, and even more preferably 0.15: 7.
[0038] In this invention, the g-C3N4 dispersion contains g-C3N4 and H4PMo 11 VO 40 H4PMo in solution 11 VO 40 The mass ratio is 100:15 to 45, specifically 100:20, 100:25, 100:30, 100:35, and 100:40.
[0039] In this invention, the mixing is H4PMo 11 VO 40 The solution was added dropwise to the g-C3N4 dispersion at a rate of 20–30 drops / min, specifically 22 drops / min, 24 drops / min, 25 drops / min, 26 drops / min, and 28 drops / min.
[0040] The present invention also provides a lignin depolymerization catalyst prepared by the preparation method described above.
[0041] This invention also provides the application of a lignin depolymerization catalyst in the depolymerization of lignin, comprising the following steps:
[0042] Lignin, a lignin depolymerization catalyst, a eutectic solvent, and water were mixed and subjected to a depolymerization reaction under light irradiation to obtain 4-butyryl-2-methoxyphenol.
[0043] In this invention, the mass-volume ratio of lignin, lignin depolymerization catalyst, eutectic solvent and water is 0.08-0.12g:0.18-0.22g:18-22mL:0.8-1.2mL, preferably 0.09-0.11g:0.19-0.21g:19-21mL:0.9-1.1mL, and more preferably 0.1g:0.2g:20mL:1mL.
[0044] In this invention, the eutectic solvent is a mixture of choline chloride and toluenesulfonic acid.
[0045] In this invention, the temperature of the depolymerization reaction is 70-100°C, specifically 75°C, 80°C, 85°C, 90°C, or 95°C; the time of the depolymerization reaction is 5-8 hours, specifically 5.5 hours, 6 hours, 6.5 hours, 7 hours, or 7.5 hours.
[0046] In this invention, a photocatalytically selective depolymerization system using HPMoV / C3N4 (lignin depolymerization catalyst) and acidic DES solvent (eutectic solvent) is employed to prepare 4-butyryl-2-methoxyphenol. The HPMoV / C3N4 photocatalyst generates photogenerated electrons and holes under illumination, overcoming the problem of low monophenol yield caused by the high viscosity of the acidic DES solvent solution inhibiting mass and heat transfer. The acidic DES solvent reacts more fully with lignin through the synergistic effect of acceptors and donors in hydrogen bonds and exposed acidic sites. This invention improves the selectivity of lignin conversion to monophenol compounds.
[0047] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0048] The methods for preparing the eutectic solvent in the embodiments described in this invention are as follows: choline chloride and p-toluenesulfonic acid (molar ratio 1:2) are mixed, heated and stirred at 80°C for 30 min until the solution is clear and transparent, thus obtaining an acidic DES solvent (eutectic solvent). The methods for preparing the eutectic solvent are not considered as limitations on this invention.
[0049] Example 1
[0050] Preparation of lignin depolymerization catalyst: First, weigh 10g of melamine into a ceramic crucible, heat in a muffle furnace at 550℃ for 2h, cool, and grind to obtain a 10-13μm g-C3N4 pale yellow powder. Take 0.5g of g-C3N4 into a beaker and add 20mL of deionized water, sonicate for 1h. Separately, take 0.125g of H4PMo... 11 VO 40 Dissolve the solution in 10 mL of a mixture of C2H5OH and H2O (volume ratio 1:1). Add this solution dropwise (25 drops / min) to the C3N4 dispersion, stir, then filter, wash, and dry to obtain a lignin depolymerization catalyst with a loading of 25% of HPMoV / C3N4 composite material.
[0051] Preparation of lignin: First, 5.0 g of defatted larch wood powder, 30 mL of 1,4-dioxane, and 0.85 mL of 37 wt% HCl were placed in a round-bottom flask. The mixture was then refluxed in an oil bath at 85 °C for 4 h. After the reaction was complete, the mixture was cooled to room temperature, and then 1.68 g of NaHCO3 was added and stirred for 30 min. The mixture was filtered, washed with 10 mL of 1,4-dioxane, and the solution was distilled under reduced pressure at 50 °C. After dilution with 10 mL of ethyl acetate, the solution was added to 50 mL of rapidly stirred n-hexane, filtered, washed with diethyl ether and H2O, and dried to obtain lignin.
[0052] Preparation of 4-butyryl-2-methoxyphenol: The photocatalytic experiment was conducted under visible light irradiation by a 220W xenon lamp. First, 0.1g of lignin and 0.2g of catalyst were added to a sealed quartz bottle, followed by 1mL of H₂O and 20mL of acidic DES solvent. The mixture was heated in a water bath at 80℃ for 6 hours. The product solution was obtained by centrifugation and extracted with ethyl acetate. The ethyl acetate layer was collected, rotary evaporated, and filtered to obtain bio-oil. The conversion rate of lignin was 70%, the bio-oil yield was 38%, and the yield of 4-butyryl-2-methoxyphenol was 11%.
[0053] Using 3,5-dimethylphenol as an internal standard, the obtained 4-butyryl-2-methoxyphenol was detected, and the results are as follows: Figure 1 As shown, from Figure 1 It can be seen that the depolymerization of lignin under the HPMoV / CN / DES system yields 4-butyryl-2-methoxyphenol, and only one monophenolic product was detected by GC-MS: 4-butyryl-2-methoxyphenol.
[0054] Example 2
[0055] Preparation of lignin depolymerization catalyst: First, weigh 10g of melamine into a ceramic crucible, heat in a muffle furnace at 550℃ for 2h, cool, and grind to obtain a 10-15μm g-C3N4 pale yellow powder. Take 0.5g of g-C3N4 into a beaker and add 25mL of deionized water, sonicate for 1h. Separately, take 0.225g of H4PMo... 11 VO 40 Dissolve it in 10 mL of a mixture of C2H5OH and H2O (volume ratio 1:1). Add this solution dropwise (30 drops / min) to the C3N4 dispersion, stir, then filter, wash, and dry to obtain an HPMoV / C3N4 composite material-lignin depolymerization catalyst with a loading of 45%.
[0056] Preparation of lignin: First, 5.0 g of defatted larch wood powder, 30 mL of 1,4-dioxane, and 0.85 mL of 37 wt% HCl were placed in a round-bottom flask. The mixture was then refluxed in an oil bath at 85 °C for 4 h. After the reaction was complete, the mixture was cooled to room temperature, and then 1.68 g of NaHCO3 was added and stirred for 30 min. The mixture was filtered, washed with 10 mL of 1,4-dioxane, and the solution was distilled under reduced pressure at 50 °C. After dilution with 10 mL of ethyl acetate, the solution was added to 50 mL of rapidly stirred n-hexane, filtered, washed with diethyl ether and H2O, and dried to obtain lignin.
[0057] Preparation of 4-butyryl-2-methoxyphenol: The photocatalytic experiment was conducted under visible light irradiation by a 220W xenon lamp. First, 0.1g of lignin and 0.2g of catalyst were added to a sealed quartz bottle, followed by 1mL of H₂O and 20mL of acidic DES solvent. The mixture was heated in a water bath at 70℃ for 8 hours. The product solution was obtained by centrifugation and extracted with ethyl acetate. The ethyl acetate layer was collected, rotary evaporated, and filtered to obtain bio-oil. The conversion rate of lignin was 68%, the bio-oil yield was 30%, and the yield of 4-butyryl-2-methoxyphenol was 10%.
[0058] Example 3
[0059] Preparation of lignin depolymerization catalyst: First, weigh 10g of melamine into a ceramic crucible, heat in a muffle furnace at 550℃ for 2h, cool, and grind to obtain a 10-15μm g-C3N4 pale yellow powder. Take 0.5g of g-C3N4 into a beaker and add 25mL of deionized water, sonicate for 1h. Separately, take 0.1g of H4PMo... 11 VO 40 Dissolve the solution in 8 mL of a mixture of C2H5OH and H2O (volume ratio 1:1). Add this solution dropwise (20 drops / min) to the C3N4 dispersion, stir, then filter, wash, and dry to obtain a 20% loaded HPMoV / C3N4 composite material-lignin depolymerization catalyst.
[0060] Preparation of lignin: First, 5.0 g of defatted larch wood powder, 30 mL of 1,4-dioxane, and 0.85 mL of 37 wt% HCl were placed in a round-bottom flask. The mixture was then refluxed in an oil bath at 85 °C for 4 h. After the reaction was complete, the mixture was cooled to room temperature, and then 1.68 g of NaHCO3 was added and stirred for 30 min. The mixture was filtered, washed with 10 mL of 1,4-dioxane, and the solution was distilled under reduced pressure at 50 °C. After dilution with 10 mL of ethyl acetate, the solution was added to 50 mL of rapidly stirred n-hexane, filtered, washed with diethyl ether and H2O, and dried to obtain lignin.
[0061] Preparation of 4-butyryl-2-methoxyphenol: The photocatalytic experiment was conducted under visible light irradiation by a 220W xenon lamp. First, 0.1g of lignin and 0.2g of catalyst were added to a sealed quartz bottle, followed by 1mL of H₂O and 20mL of acidic DES solvent. The mixture was heated in a water bath at 100℃ for 5 hours. The product solution was obtained by centrifugation and extracted with ethyl acetate. The ethyl acetate layer was collected, rotary evaporated, and filtered to obtain bio-oil. The conversion rate of lignin was 68%, the bio-oil yield was 35%, and the yield of 4-butyryl-2-methoxyphenol was 9%.
[0062] Comparative Example 1
[0063] The only difference between this comparative example and Example 1 is that it uses the same mass of HPMoV (H4PMo). 11 VO 40 Using [catalyst], the conversion rate of lignin was 55%, the bio-oil yield was 31%, and the yield of 4-butyryl-2-methoxyphenol was 5%.
[0064] Comparative Example 2
[0065] The only difference between this comparative example and Example 1 is the use of an equal mass of CN (g-C3N4) as a catalyst. The lignin conversion rate was 54%, the bio-oil yield was 31%, and the 4-butyryl-2-methoxyphenol yield was 5%.
[0066] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.
[0067] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims
1. The application of a lignin depolymerization catalyst in the depolymerization of lignin, characterized in that, Includes the following steps: Lignin, lignin depolymerization catalyst, eutectic solvent and water were mixed and depolymerized under light conditions to obtain 4-butyryl-2-methoxyphenol. The preparation method of the lignin depolymerization catalyst is as follows: The g-C3N4 dispersion was mixed with H4PMo 11 VO 40 The solutions were mixed and dried to obtain a lignin depolymerization catalyst.
2. The application of the lignin depolymerization catalyst according to claim 1 in the depolymerization of lignin, characterized in that, The mass-volume ratio of lignin, lignin depolymerization catalyst, eutectic solvent and water is 0.08~0.12g:0.18~0.22g:18~22mL:0.8~1.22mL.
3. The application of the lignin depolymerization catalyst according to claim 1 in the depolymerization of lignin, characterized in that, The eutectic solvent is a mixture of choline chloride and toluenesulfonic acid.
4. The application of the lignin depolymerization catalyst according to any one of claims 1 to 3 in the depolymerization of lignin, characterized in that, The depolymerization reaction is carried out at a temperature of 70~100℃ for 5~8 hours.