Preparation method of lignin nanoparticle liquid-phase dispersion or solid dispersion

Abstract

The invention discloses a lignin nanoparticle liquid-phase dispersion or solid dispersion preparation method which comprises the following steps: 1) adding lignin into a good solvent, stirring and dissolving to form feed liquid A; or adding the lignin and the surfactant into a good solvent, stirring and dissolving to form feed liquid A; 2) adding a surfactant into a poor solvent, stirring and dissolving to form a feed liquid B; or a poor solvent is used as feed liquid B; 3) introducing the feed liquid A and the feed liquid B into a supergravity rotating packed bed through a peristaltic pump, and precipitating to obtain a lignin nanoparticle suspension; 4) centrifuging and washing the lignin nanoparticle suspension, and dispersing the lignin nanoparticle suspension in a liquid to obtain a lignin nanoparticle liquid-phase dispersion; or carrying out rotary evaporation on the lignin nanoparticle suspension to obtain the lignin nanoparticle liquid-phase dispersion. The prepared lignin nano-particle liquid-phase dispersion is good in stability and narrow in particle size distribution, and the particle size of the particles ranges from 5 nm to 50 nm.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterial preparation technology, and in particular relates to a method for preparing lignin nanoparticle liquid or solid dispersions. Background Technology

[0002] Nanomaterials, due to their high specific surface area, quantum effects, and unique physicochemical properties, show broad application prospects in energy, medicine, environmental protection, and other fields. Lignin, as the second most abundant renewable aromatic polymer in nature (accounting for 15-30% of plant dry weight), possesses characteristics such as biodegradability, antioxidant properties, UV shielding, and high thermal stability. However, its naturally occurring structural heterogeneity, molecular weight polydispersity, and hydrophobicity limit its macroscopic applications. Nanoparticles of lignin can significantly overcome these shortcomings: lignin nanoparticles have uniform morphology, excellent stability, and a high density of surface functional groups (such as phenolic hydroxyl and carboxyl groups), which not only enhances compatibility with polymer matrices but also provides an ideal platform for drug loading, catalysis, and composite material reinforcement.

[0003] Existing literature has reported numerous preparation processes for lignin nanoparticles, including self-assembly, acid precipitation, antisolvent precipitation, interfacial crosslinking, hydrothermal synthesis, ultrasonic disruption, and biosynthesis. However, due to the structural heterogeneity and polydispersity of lignin, the preparation conditions for lignin nanoparticles are particularly demanding, and the resulting lignin nanoparticles still suffer from problems such as difficulty in reducing size, poor dispersibility, low versatility, low yield, and slow reaction time.

[0004] For example, Chinese patent application CN202310361621 discloses a technical solution entitled "A method for preparing a colloidal dispersion of lignin nanoparticles with uniform size and good stability and its application." This solution involves dissolving hydrophilic sulfate lignin in a THF / water mixture (vTHF / vwater = 7 / 3), reducing the solubility of lignin with water, and then further treating it by rotary evaporation to obtain a colloidal dispersion of lignin nanoparticles. While this method is simple to operate, the preparation process is overly cumbersome, the yield is too low, limiting production efficiency and making industrial-scale production difficult.

[0005] For example, Chinese patent application CN119372948A discloses a technical solution entitled "A method and application for preparing multi-scale nano-lignin waterproof and oil-resistant agent using alkaline pulping black liquor". This technical solution directly obtains lignin nanoparticles from alkaline pulping black liquor through acid precipitation. However, the obtained lignin nanoparticles have a wide size distribution, the particle size is difficult to control, and freeze-drying is required, making it difficult to scale up for industrial production.

[0006] For example, Chinese patent application CN120309974A discloses a technical solution entitled "A high-purity submicron or nano lignin and its preparation method". This technical solution utilizes microwave heating technology, with a heating time exceeding 6 hours, resulting in a long preparation time, high energy consumption, and a wide size distribution and irregular morphology of the obtained lignin nanoparticles.

[0007] For example, Chinese patent application CN116322963A discloses a technical solution entitled "A Method for Preparing a Colloidal Dispersion of Sulfate Lignin Nanoparticles." This technical solution mainly involves dissolving sulfate lignin in a solvent, and then mixing the aforementioned solution with an antisolvent under mixed conditions to obtain a colloidal dispersion of nanoparticles. The average diameter of the nanoparticles ranges from 9 nm to 70 nm. However, the nanoparticles prepared by this technical solution still suffer from a wide particle size distribution (DLS analysis showed that the intensity of each size did not exceed 20%).

[0008] In order to address the existing shortcomings and accelerate the large-scale preparation and industrial application of lignin nanoparticles, it is urgent to develop a method for preparing liquid or solid dispersions of lignin nanoparticles with good versatility. Summary of the Invention

[0009] The first technical problem this invention aims to solve is to provide a method for preparing a liquid dispersion of lignin nanoparticles. This method utilizes a hypergravity device to enhance the antisolvent precipitation reaction, which not only shortens the reaction time and improves production efficiency, but also facilitates large-scale production. Furthermore, the resulting liquid dispersion of lignin nanoparticles exhibits good stability and a narrow particle size distribution, with particle sizes ranging from 5 to 50 nm. Compared to other preparation methods, the hypergravity rotating packed bed can operate continuously, making it easy to achieve large-scale industrial production.

[0010] The second technical problem to be solved by this invention is to provide a method for preparing a lignin nanoparticle solid dispersion. The lignin nanoparticle suspension obtained in the above-mentioned liquid dispersion preparation process is passed through a spray dryer for spray drying to obtain the corresponding lignin nanoparticle solid dispersion; or the wet solid after centrifugation and washing of the lignin nanoparticle suspension is vacuum dried to obtain the corresponding lignin nanoparticle solid dispersion. Its particle size is between 5 and 50 nm, approximately spherical, with a narrow particle size distribution and uniform morphology.

[0011] In summary, this invention applies supergravity technology to prepare a liquid or solid dispersion of lignin nanoparticles, which has the characteristics of good stability, narrow particle size distribution, and uniform morphology.

[0012] To solve the first technical problem mentioned above, the technical solution adopted by the present invention is as follows: :

[0013] A method for preparing a lignin nanoparticle liquid dispersion includes the following steps:

[0014] 1) Add lignin to a good solvent, stir to dissolve, and form solution A; or add lignin and surfactant to a good solvent, stir to dissolve, and form solution A;

[0015] 2) Add the surfactant to the unsuitable solvent, stir to dissolve, and form solution B; or use the unsuitable solvent as solution B;

[0016] 3) Feed solution A and feed solution B are fed into a high-gravity rotating packed bed through a peristaltic pump, and after precipitation, a lignin nanoparticle suspension is obtained.

[0017] 4) Centrifuge and wash the lignin nanoparticle suspension and disperse it in a liquid to obtain a lignin nanoparticle liquid dispersion; or rotary evaporate the lignin nanoparticle suspension to obtain a lignin nanoparticle liquid dispersion.

[0018] As a further improvement to the technical solution, in step 1), the lignin is one of alkali lignin, enzymatically hydrolyzed lignin, sulfate lignin, organic solvent lignin, and lignin sulfonate; preferably, the lignin is one of alkali lignin and enzymatically hydrolyzed lignin; more preferably, the lignin is alkali lignin.

[0019] Preferably, in step 1), the good solvent is selected from one or more of the following substances: water, aqueous sodium hydroxide solution, methanol, ethanol, ethylene glycol, N,N-dimethylformamide, acetone, tetrahydrofuran, γ-valerolactone, dimethyl sulfoxide, dichloromethane, and glycerol; preferably, the good solvent is one or more of water, aqueous sodium hydroxide solution, acetone, and γ-valerolactone; more preferably, the good solvent is water or aqueous sodium hydroxide solution.

[0020] Preferably, in step 1), the stirring temperature is 10–80°C and the stirring time is 5–60 min.

[0021] Preferably, in step 1), the concentration of lignin in the liquid A is 1 to 120 g / L.

[0022] As a further improvement to the technical solution, in step 1) or step 2), the surfactant is selected from one or more of the following substances: lignin sulfonate, sodium dodecyl sulfonate, sodium dodecyl sulfate, polyethylene glycol, polyvinylpyrrolidone, hydroxypropyl methylcellulose, dodecyltrimethylammonium bromide, cyclodextrin, mannitol, γ-aminopropyltriethoxysilane, γ-methacryloyloxypropyltrimethoxysilane; preferably, the surfactant is one or more of lignin sulfonate, sodium dodecyl sulfonate, polyvinylpyrrolidone, and sodium dodecyl sulfate; more preferably, the surfactant is lignin sulfonate.

[0023] Preferably, in step 1) or step 2), the amount of surfactant used is 0-20% of the mass of lignin.

[0024] As a further improvement to the technical solution, preferably, in step 2), the unsuitable solvent is selected from one or more of the following substances: 0.01-2.5 mol / L hydrochloric acid solution, 0.01-2.5 mol / L sulfuric acid solution, 0.01-2.5 mol / L acetic acid, 0.01-2.5 mol / L phosphoric acid, 0.01-2.5 mol / L oxalic acid, water, methanol, ethanol, isopropanol, and glycerol; more preferably, the unsuitable solvent is one or more of 0.01-2.5 mol / L hydrochloric acid solution, 0.01-2.5 mol / L sulfuric acid solution, and water; even more preferably, the unsuitable solvent is 0.01-2.5 mol / L hydrochloric acid solution.

[0025] Preferably, in step 2), the stirring temperature is 10–80°C and the stirring time is 5–60 min.

[0026] As a further improvement to the technical solution, in step 3), the reaction temperature inside the supergravity rotating packed bed is 10–90°C; more preferably, the temperature is 10–60°C.

[0027] Preferably, in step 3), the feed flow rate of liquid A is 20-800 mL / min, and the feed flow rate of liquid B is 200-2000 mL / min.

[0028] Preferably, in step 3), the ratio of feed flow rates of liquid A to liquid B is 1:1 to 1:40.

[0029] Preferably, in step 3), the rotor speed of the supergravity rotating filling bed is 300 to 3000 rpm.

[0030] As a further improvement to the technical solution, in step 4), the centrifugation speed is 6000-12000 rpm; the centrifugation time is 3-15 min.

[0031] Preferably, in step 4), the solvent used for washing is selected from one or more of the following substances: water, acid solution with pH = 2 to 5, methanol, ethanol, glycerol, isopropanol, acetone, and ethyl acetate.

[0032] Preferably, in step 4), the liquid is selected from one or more of the following substances: water, an acid solution with pH = 2 to 5, methanol, ethanol, isopropanol, acetone, and ethyl acetate; preferably, the liquid is one or more of water, an acid solution with pH = 2 to 5, methanol, and ethanol; more preferably, the liquid is an acid solution with pH = 2 to 5.

[0033] Preferably, in step 4), the temperature of the rotary evaporator is 25–85°C and the rotation speed is 10–80 rpm.

[0034] To solve the second technical problem mentioned above, the technical solution adopted by the present invention is as follows: :

[0035] A method for preparing a lignin nanoparticle solid dispersion includes the following steps:

[0036] 11) Add lignin to a good solvent, stir to dissolve, and form solution A; or add lignin and surfactant to a good solvent, stir to dissolve, and form solution A;

[0037] 12) Add the surfactant to the unsuitable solvent, stir to dissolve, and form solution B; or use the unsuitable solvent as solution B;

[0038] 13) Feed solution A and feed solution B are fed into a high-gravity rotating packed bed through a peristaltic pump, and after precipitation, a lignin nanoparticle suspension is obtained.

[0039] 14) The lignin nanoparticle suspension is passed into a spray dryer for spray drying to obtain the corresponding solid dispersion; or the lignin nanoparticle suspension is centrifuged, washed, and the wet solid is vacuum dried to obtain the lignin nanoparticle solid dispersion.

[0040] As a further improvement to the technical solution, in step 11), the lignin is one of alkali lignin, enzymatically hydrolyzed lignin, sulfate lignin, organic solvent lignin, and lignin sulfonate; preferably, the lignin is one of alkali lignin and enzymatically hydrolyzed lignin; more preferably, the lignin is alkali lignin.

[0041] Preferably, in step 11), the good solvent is selected from one or more of the following substances: water, aqueous sodium hydroxide solution, methanol, ethanol, ethylene glycol, N,N-dimethylformamide, acetone, tetrahydrofuran, γ-valerol, dimethyl sulfoxide, dichloromethane, and glycerol; preferably, the good solvent is one or more of water, aqueous sodium hydroxide solution, acetone, and γ-valerol; more preferably, the good solvent is water or aqueous sodium hydroxide solution.

[0042] Preferably, in step 11), the stirring temperature is 10–80°C and the stirring time is 5–60 min.

[0043] Preferably, in step 11), the concentration of lignin in the liquid A is 1 to 120 g / L.

[0044] As a further improvement to the technical solution, in step 11) or step 12), the surfactant is selected from one or more of the following substances: sodium dodecyl sulfonate, sodium dodecyl sulfate, polyethylene glycol, polyvinylpyrrolidone, hydroxypropyl methylcellulose, dodecyltrimethylammonium bromide, cyclodextrin, mannitol, γ-aminopropyltriethoxysilane, γ-methacryloyloxypropyltrimethoxysilane; preferably, the surfactant is one or more of lignin sulfonate, sodium dodecyl sulfonate, polyvinylpyrrolidone, and sodium dodecyl sulfate; more preferably, the surfactant is lignin sulfonate.

[0045] Preferably, in step 11) or step 12), the amount of surfactant used is 0-20% of the mass of lignin.

[0046] Preferably, in step 12), the unsuitable solvent is selected from one or more of the following substances: 0.01–2.5 mol / L hydrochloric acid solution, 0.01–2.5 mol / L sulfuric acid solution, 0.01–2.5 mol / L acetic acid, 0.01–2.5 mol / L phosphoric acid, 0.01–2.5 mol / L oxalic acid, water, methanol, ethanol, isopropanol, and glycerol; more preferably, the unsuitable solvent is one or more of 0.01–2.5 mol / L hydrochloric acid solution, 0.01–2.5 mol / L sulfuric acid solution, and water; even more preferably, the unsuitable solvent is 0.01–2.5 mol / L hydrochloric acid solution.

[0047] Preferably, in step 12), the stirring temperature is 10–80°C and the stirring time is 5–60 min.

[0048] As a further improvement to the technical solution, in step 13), the reaction temperature inside the supergravity rotating packed bed is 10–90°C; more preferably, the temperature is 10–60°C.

[0049] Preferably, in step 13), the feed flow rate of liquid A is 20-800 mL / min, and the feed flow rate of liquid B is 200-2000 mL / min.

[0050] Preferably, in step 13), the ratio of feed flow rates of liquid A to liquid B is 1:1 to 1:40.

[0051] Preferably, in step 13), the rotor speed of the supergravity rotating filling bed is 300 to 3000 rpm.

[0052] As a further improvement to the technical solution, in step 14), the centrifugation speed is 6000-12000 rpm; the centrifugation time is 3-15 min.

[0053] Preferably, in step 14), the solvent used for washing is selected from one or more of the following substances: water, acid solution with pH = 2 to 5, methanol, ethanol, glycerol, isopropanol, acetone, and ethyl acetate.

[0054] Preferably, in step 14), the liquid is selected from one or more of the following substances: water, an acid solution with pH = 2 to 5, methanol, ethanol, isopropanol, acetone, and ethyl acetate; preferably, the liquid is one or more of water, an acid solution with pH = 2 to 5, methanol, and ethanol; more preferably, the liquid is an acid solution with pH = 2 to 5.

[0055] Preferably, in step 14), the temperature of the rotary evaporation is 25-85°C and the rotation speed is 10-80 rpm.

[0056] Any range described in this invention includes the endpoint, any value between the endpoints, and any subrange consisting of the endpoint or any value between the endpoints.

[0057] Unless otherwise specified, all raw materials used in this invention can be obtained commercially, and the equipment used in this invention can be conventional equipment in the relevant field or refer to existing technology in the relevant field.

[0058] Compared with the prior art, the present invention has the following beneficial effects:

[0059] 1) The process of this invention is simple, easy to operate, highly repeatable, and easy to scale up; the precipitation reaction is completed instantaneously in the supergravity reactor, resulting in high production efficiency and suitability for large-scale production.

[0060] 2) The lignin nanoparticles synthesized in this invention have good stability (no agglomeration after ≥180 days), narrow particle size distribution (PDI between 0.06 and 1.3), and particle size between 5 and 50 nm.

[0061] 3) The nano-sized lignin of this invention has application potential in multiple fields such as drug loading, catalysis and composite materials. Attached Figure Description

[0062] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0063] Figure 1 A schematic diagram of a hypergravity reactor used in the present invention is shown;

[0064] Figure 2 This shows a scanning electron microscope image of the alkali lignin raw material used in this invention;

[0065] Figure 3 This shows a scanning electron microscope image of the alkali lignin nanoparticles obtained in Example 1 of the present invention;

[0066] Figure 4 The particle size distribution diagram of the alkali lignin nanoparticles obtained in Example 1 of the present invention is shown.

[0067] Figure 5 This shows a transmission electron microscope image of the alkali lignin nanoparticles obtained in Example 3 of the present invention;

[0068] Figure 6 This shows a scanning electron microscope image of the alkali lignin nanoparticles obtained in Example 5 of the present invention;

[0069] Figure 7 The particle size distribution diagram of the alkali lignin nanoparticles obtained in Example 5 of the present invention is shown.

[0070] Figure 8 This shows a transmission electron microscope image of the alkali lignin nanoparticles obtained in Example 7 of the present invention;

[0071] Figure 9 The image shows a scanning electron microscope (SEM) image of the alkali lignin nanoparticles obtained in Comparative Example 2 of the present invention.

[0072] Figure 10 The particle size distribution diagram of the alkali lignin nanoparticles obtained in Comparative Example 2 of the present invention is shown.

[0073] Figure 11 The image shown is a scanning electron microscope image of the alkali lignin nanoparticles obtained in Comparative Example 4 of the present invention. Detailed Implementation

[0074] To more clearly illustrate the present invention, the following description, in conjunction with preferred embodiments, further clarifies the invention. Those skilled in the art should understand that the specific descriptions below are illustrative rather than restrictive, and should not be construed as limiting the scope of protection of the present invention.

[0075] As one aspect of the present invention, a method for preparing a lignin nanoparticle liquid dispersion includes the following steps:

[0076] 1) Add lignin to a good solvent, stir to dissolve, and form solution A; or add lignin and surfactant to a good solvent, stir to dissolve, and form solution A;

[0077] 2) Add the surfactant to the unsuitable solvent, stir to dissolve, and form solution B; or use the unsuitable solvent as solution B;

[0078] 3) Feed solution A and feed solution B are fed into a high-gravity rotating packed bed through a peristaltic pump, and after precipitation, a lignin nanoparticle suspension is obtained.

[0079] 4) Centrifuge and wash the lignin nanoparticle suspension and disperse it in a liquid to obtain a lignin nanoparticle liquid dispersion; or rotary evaporate the lignin nanoparticle suspension to obtain a lignin nanoparticle liquid dispersion.

[0080] According to certain embodiments of the present invention, in step 1), the lignin is one of alkali lignin, enzymatically hydrolyzed lignin, sulfate lignin, organic solvent lignin, and lignin sulfonate; preferably, the lignin is one of alkali lignin, enzymatically hydrolyzed lignin, and organic solvent lignin; more preferably, the lignin is alkali lignin.

[0081] According to certain embodiments of the present invention, in step 1), the good solvent is selected from one or more of the following substances: water, aqueous sodium hydroxide solution, methanol, ethanol, ethylene glycol, N,N-dimethylformamide, acetone, tetrahydrofuran, γ-valerol, dimethyl sulfoxide, dichloromethane, and glycerol; preferably, the good solvent is one or more of water, aqueous sodium hydroxide solution, acetone, and γ-valerol; more preferably, the good solvent is water or aqueous sodium hydroxide solution.

[0082] According to certain embodiments of the present invention, in step 1), the stirring temperature is 10-80°C and the stirring time is 5-60 min.

[0083] According to certain embodiments of the present invention, in step 1), the concentration of lignin in the liquid A is preferably 1 to 120 g / L.

[0084] According to certain embodiments of the present invention, in step 2), the surfactant is selected from one or more of the following substances: lignin sulfonate, sodium dodecyl sulfonate, sodium dodecyl sulfate, polyethylene glycol, polyvinylpyrrolidone, hydroxypropyl methylcellulose, dodecyltrimethylammonium bromide, cyclodextrin, mannitol, γ-aminopropyltriethoxysilane, γ-methacryloyloxypropyltrimethoxysilane; preferably, the surfactant is one or more of lignin sulfonate, sodium dodecyl sulfonate, polyvinylpyrrolidone, and sodium dodecyl sulfate; more preferably, the surfactant is lignin sulfonate.

[0085] According to certain embodiments of the present invention, in step 2), the amount of surfactant used is 0-20% of the mass of lignin.

[0086] According to certain embodiments of the present invention, in step 2), the unsuitable solvent is selected from one or more of the following substances: 0.01–2.5 mol / L hydrochloric acid solution, 0.01–2.5 mol / L sulfuric acid solution, 0.01–2.5 mol / L acetic acid, 0.01–2.5 mol / L phosphoric acid, 0.01–2.5 mol / L oxalic acid, water, methanol, ethanol, isopropanol, and glycerol; more preferably, the unsuitable solvent is one or more of 0.01–2.5 mol / L hydrochloric acid solution, 0.01–2.5 mol / L sulfuric acid solution, and water; even more preferably, the unsuitable solvent is 0.01–2.5 mol / L hydrochloric acid solution.

[0087] According to some embodiments of the present invention, in step 2), the stirring temperature is 10-80°C and the stirring time is 5-60 min.

[0088] According to certain embodiments of the present invention, in step 3), the reaction temperature inside the supergravity rotating packed bed is 10–90°C; more preferably, the temperature is 10–60°C.

[0089] According to certain embodiments of the present invention, in step 3), the feed flow rate of liquid A is 20-800 mL / min, and the feed flow rate of liquid B is 200-2000 mL / min.

[0090] According to certain embodiments of the present invention, in step 3), the ratio of feed flow rates of liquid A to liquid B is 1:1 to 1:40.

[0091] According to certain embodiments of the present invention, in step 3), the rotor speed of the supergravity rotating filling bed is 300 to 3000 rpm.

[0092] According to some embodiments of the present invention, in step 4), the centrifugation speed is 6000-12000 rpm; the centrifugation time is 3-15 min.

[0093] According to certain embodiments of the present invention, in step 4), the solvent used for washing is selected from one or more of the following substances: water, acid solution with pH = 2 to 5, methanol, ethanol, glycerol, isopropanol, acetone, and ethyl acetate.

[0094] According to certain embodiments of the present invention, in step 4), the liquid is selected from one or more of the following substances: water, an acid solution with pH = 2 to 5, methanol, ethanol, isopropanol, acetone, and ethyl acetate; preferably, the liquid is one or more of water, an acid solution with pH = 2 to 5, methanol, and ethanol; more preferably, the liquid is an acid solution with pH = 2 to 5.

[0095] According to certain embodiments of the present invention, in step 4), the temperature of the rotary evaporation is 25-85°C and the rotation speed is 10-80 rpm.

[0096] As another aspect of the present invention, a method for preparing a lignin nanoparticle solid dispersion includes the following steps:

[0097] 11) Add lignin to a good solvent, stir to dissolve, and form solution A; or add lignin and surfactant to a good solvent, stir to dissolve, and form solution A;

[0098] 12) Add the surfactant to the unsuitable solvent, stir to dissolve, and form solution B; or use the unsuitable solvent as solution B;

[0099] 13) Feed solution A and feed solution B are fed into a high-gravity rotating packed bed through a peristaltic pump, and after precipitation, a lignin nanoparticle suspension is obtained.

[0100] 14) The lignin nanoparticle suspension is passed into a spray dryer for spray drying to obtain the corresponding solid dispersion; or the lignin nanoparticle suspension is centrifuged, washed, and the wet solid is vacuum dried to obtain the lignin nanoparticle solid dispersion.

[0101] According to certain embodiments of the present invention, in step 11), the lignin is one of alkali lignin, enzymatically hydrolyzed lignin, sulfate lignin, organic solvent lignin, and lignin sulfonate; preferably, the lignin is one of alkali lignin and enzymatically hydrolyzed lignin; more preferably, the lignin is alkali lignin.

[0102] According to certain embodiments of the present invention, in step 11), the good solvent is selected from one or more of the following substances: water, aqueous sodium hydroxide solution, methanol, ethanol, ethylene glycol, N,N-dimethylformamide, acetone, tetrahydrofuran, γ-valerolactone, dimethyl sulfoxide, dichloromethane, and glycerol; preferably, the good solvent is one or more of water, aqueous sodium hydroxide solution, acetone, and γ-valerolactone; more preferably, the good solvent is water or aqueous sodium hydroxide solution.

[0103] According to certain embodiments of the present invention, in step 11), the stirring temperature is 10-80°C and the stirring time is 5-60 min.

[0104] According to certain embodiments of the present invention, in step 11), the concentration of lignin in the liquid A is preferably 1 to 120 g / L.

[0105] According to certain embodiments of the present invention, in step 11) or step 12), the surfactant is selected from one or more of the following substances: sodium dodecyl sulfonate, sodium dodecyl sulfate, polyethylene glycol, polyvinylpyrrolidone, hydroxypropyl methylcellulose, dodecyltrimethylammonium bromide, cyclodextrin, mannitol, γ-aminopropyltriethoxysilane, γ-methacryloyloxypropyltrimethoxysilane; preferably, the surfactant is one or more of lignin sulfonate, sodium dodecyl sulfonate, polyvinylpyrrolidone, and sodium dodecyl sulfate; more preferably, the surfactant is lignin sulfonate.

[0106] According to certain embodiments of the present invention, in step 11) or step 12), the amount of the surfactant is 0 to 20% of the mass of the lignin.

[0107] According to certain embodiments of the present invention, in step 12), the unsuitable solvent is selected from one or more of the following substances: 0.01–2.5 mol / L hydrochloric acid solution, 0.01–2.5 mol / L sulfuric acid solution, 0.01–2.5 mol / L acetic acid, 0.01–2.5 mol / L phosphoric acid, 0.01–2.5 mol / L oxalic acid, water, methanol, ethanol, isopropanol, and glycerol; more preferably, the unsuitable solvent is one or more of 0.01–2.5 mol / L hydrochloric acid solution, 0.01–2.5 mol / L sulfuric acid solution, and water; even more preferably, the unsuitable solvent is 0.01–2.5 mol / L hydrochloric acid solution.

[0108] According to certain embodiments of the present invention, in step 12), the stirring temperature is 10-80°C and the stirring time is 5-60 min.

[0109] According to certain embodiments of the present invention, in step 13), the reaction temperature inside the supergravity rotating packed bed is 10–90°C; more preferably, the temperature is 10–60°C.

[0110] According to certain embodiments of the present invention, in step 13), the feed flow rate of liquid A is 20-800 mL / min, and the feed flow rate of liquid B is 200-2000 mL / min.

[0111] According to certain embodiments of the present invention, in step 13), the ratio of feed flow rates of liquid A to liquid B is 1:1 to 1:40.

[0112] According to certain embodiments of the present invention, in step 13), the rotor speed of the supergravity rotating filling bed is 300 to 3000 rpm.

[0113] According to certain embodiments of the present invention, in step 14), the centrifugation speed is 6000-12000 rpm; the centrifugation time is 3-15 min.

[0114] According to certain embodiments of the present invention, in step 14), the solvent used for washing is selected from one or more of the following substances: water, acid solution with pH = 2 to 5, methanol, ethanol, glycerol, isopropanol, acetone, and ethyl acetate.

[0115] According to certain embodiments of the present invention, in step 14), the liquid is selected from one or more of the following substances: water, an acid solution with pH = 2 to 5, methanol, ethanol, isopropanol, acetone, and ethyl acetate; preferably, the liquid is one or more of water, an acid solution with pH = 2 to 5, methanol, and ethanol; more preferably, the liquid is an acid solution with pH = 2 to 5.

[0116] According to certain embodiments of the present invention, in step 14), the temperature of the rotary evaporation is 25-85°C and the rotation speed is 10-80 rpm.

[0117] The supergravity rotating packed bed used in this invention is an existing one, such as the published Chinese patent application publication number: CN2221437A, invention title "Rotating Bed Supergravity Field Device for Enhancing Transfer Response"; Figure 1 This is a schematic diagram of a conventional hypergravity reactor used in this invention. The specific implementation of the hypergravity reactor is as follows: The hypergravity reactor device is turned on, and the rotation speed is adjusted to bring the rotor speed inside the device to a preset value; liquid A is introduced into the feed inlet 1 of the hypergravity reactor through a peristaltic pump; liquid B is introduced into the feed inlet 2 of the hypergravity reactor through a peristaltic pump; the rotor packing 3 inside the hypergravity reactor is driven by a motor 4 and rotates at high speed, thereby obtaining a hypergravity environment; liquids A and B are sprayed onto the inner edge of the rotor packing of the hypergravity reactor through a liquid distributor on the feed pipe, colliding with the packing and entering the packing interior; liquids A and B inside the packing are divided, broken, and torn by the wire mesh packing, generating a large amount of rapidly... The updated liquid surface greatly enhances the intermolecular mass transfer process, shortens the nucleus growth time after reactant precipitation and crystallization, and thus effectively controls the particle size and morphology of nucleated particles. The solution after the reaction flows out from the liquid phase outlet 5 at the bottom of the supergravity reactor. The lignin nanoparticle suspension flowing out of the outlet is collected, centrifuged, washed, and rotary evaporated, and then dispersed in the liquid to obtain a clean lignin nanoparticle liquid phase dispersion. The lignin nanoparticle suspension is spray-dried to obtain a lignin nanoparticle solid dispersion; or the lignin nanoparticle suspension is centrifuged, washed, and the wet solid is vacuum dried to obtain a lignin nanoparticle solid dispersion.

[0118] Example 1

[0119] A method for preparing a liquid dispersion of alkali lignin nanoparticles includes the following steps:

[0120] 1) Dissolve 20g of alkali lignin and 0.2g of sodium lignin sulfonate in 100mL of water to make solution A;

[0121] 2) Use 100 mL of 0.07 mol / L hydrochloric acid as feed solution B;

[0122] 3) Start the high-gravity rotating packed bed reactor and set the rotor speed to 1500 rpm;

[0123] 4) Simultaneously feed liquid A and liquid B into the high gravity rotating packed bed reactor using a peristaltic pump. The feed rate of liquid A is 500 mL / min and the feed rate of liquid B is 500 mL / min. The resulting alkali lignin nanoparticle suspension is obtained after the reaction.

[0124] 5) The alkali lignin nanoparticle suspension was centrifuged and acid-washed twice, each time at a speed of 10,000 rpm for 10 min; then the centrifuged wet solid was dispersed in an acidic solution with pH = 2-5 to form a liquid dispersion of alkali lignin nanoparticles with a solid content of 5 wt%.

[0125] Figure 3 and Figure 4 The images shown are scanning electron microscope (SEM) images and particle size distribution diagrams of the alkali lignin nanoparticles from Example 1. Testing revealed that the alkali lignin nanoparticles exhibited good stability (no aggregation after 180 days of storage), a narrow particle size distribution (PDI of 0.11), and a particle size of 17 nm.

[0126] Example 2

[0127] A method for preparing an alkali lignin nanoparticle solid dispersion includes the following steps:

[0128] 1) Dissolve 20g of alkali lignin and 0.2g of sodium lignin sulfonate in 100mL of water to make solution A;

[0129] 2) Use 100 mL of 0.07 mol / L hydrochloric acid as feed solution B;

[0130] 3) Start the high-gravity rotating packed bed reactor and set the rotor speed to 1500 rpm;

[0131] 4) Simultaneously feed liquid A and liquid B into the high gravity rotating packed bed reactor using a peristaltic pump. The feed rate of liquid A is 500 mL / min and the feed rate of liquid B is 500 mL / min. The resulting alkali lignin nanoparticle suspension is obtained after the reaction.

[0132] 5) The temperature at the nozzle of the spray dryer is 180℃, the air velocity at the nozzle is 530L / h, and the peristaltic pump feeds the alkali lignin nanoparticle suspension into the spray dryer at a rate of 0.35L / h to obtain a solid dispersion of alkali lignin nanoparticles.

[0133] Testing revealed that the alkali lignin nanoparticles exhibited good stability (no significant changes in morphology and size after 180 days of storage), a narrow particle size distribution (PDI of 0.13), and a particle size of 35 nm.

[0134] Example 3

[0135] A method for preparing a liquid dispersion of alkali lignin nanoparticles includes the following steps:

[0136] 1) Dissolve 20g of alkali lignin in 100mL of 70% acetone solution to obtain solution A;

[0137] 2) Dissolve 2g of sodium dodecyl sulfonate in 2000mL of water to make solution B;

[0138] 3) Start the high-gravity rotating packed bed reactor and set the rotor speed to 1500 rpm;

[0139] 4) Simultaneously feed liquid A and liquid B into the high gravity rotating packed bed reactor using a peristaltic pump. The feed rate of liquid A is 50 mL / min and the feed rate of liquid B is 1000 mL / min. The resulting alkali lignin nanoparticle suspension is obtained after the reaction.

[0140] 5) The alkali lignin nanoparticle suspension was rotary evaporated at 40℃ and 50rpm to remove acetone, forming a liquid dispersion of alkali lignin nanoparticles with a solid content of 5wt%.

[0141] Figure 5 This is a transmission electron microscope (TEM) image of the alkali lignin nanoparticles from Example 3. Testing showed that the alkali lignin nanoparticles exhibited good stability (no aggregation after 180 days of storage), a narrow particle size distribution (PDI of 0.1), and a particle size of 10 nm.

[0142] Example 4

[0143] A method for preparing an alkali lignin nanoparticle solid dispersion includes the following steps:

[0144] 1) Dissolve 20g of alkali lignin in 100mL of 70% acetone solution to obtain solution A;

[0145] 2) Dissolve 2g of sodium dodecyl sulfonate in 2000mL of water to make solution B;

[0146] 3) Start the high-gravity rotating packed bed reactor and set the rotor speed to 1500 rpm;

[0147] 4) Simultaneously feed liquid A and liquid B into the high gravity rotating packed bed reactor using a peristaltic pump. The feed rate of liquid A is 50 mL / min and the feed rate of liquid B is 1000 mL / min. The resulting alkali lignin nanoparticle suspension is obtained after the reaction.

[0148] 5) The temperature at the nozzle of the spray dryer is 180℃, the air velocity at the nozzle is 530L / h, and the peristaltic pump feeds the alkali lignin nanoparticle suspension into the spray dryer at a rate of 0.35L / h to obtain a solid dispersion of alkali lignin nanoparticles.

[0149] Testing revealed that the alkali lignin nanoparticles exhibited good stability (no significant changes in morphology and size after 180 days of storage), a narrow particle size distribution (PDI of 0.12), and a particle size of 25 nm.

[0150] Example 5

[0151] Repeat Example 1, except that the 0.07 mol / L hydrochloric acid is replaced with 0.035 mol / L sulfuric acid.

[0152] Figure 6 and Figure 7 The images shown are scanning electron microscope (SEM) images and particle size distribution diagrams of the alkali lignin nanoparticles produced in Example 5. The particle size of the alkali lignin nanoparticles is approximately 22 nm, slightly larger than that of the alkali lignin nanoparticles prepared with hydrochloric acid.

[0153] Example 6

[0154] Repeat Example 2, except that the 0.07 mol / L hydrochloric acid is replaced with 0.035 mol / L sulfuric acid.

[0155] Tests showed that the particle size of the alkali lignin nanoparticles was approximately 50 nm, which is slightly larger than that of the alkali lignin nanoparticles prepared with hydrochloric acid.

[0156] Example 7

[0157] Example 3 was repeated, except that sodium dodecyl sulfonate was replaced with polyvinylpyrrolidone.

[0158] Figure 8 This is a transmission electron microscope (TEM) image of the alkali lignin nanoparticles from Example 7. The test results are similar to those of Example 3.

[0159] Example 8

[0160] Example 4 was repeated, except that sodium dodecyl sulfonate was replaced with polyvinylpyrrolidone.

[0161] The test results were similar to those of Example 4.

[0162] Example 9

[0163] Example 3 was repeated, except that sodium dodecyl sulfonate was replaced with sodium dodecyl sulfate.

[0164] The test results were similar to those of Example 3.

[0165] Example 10

[0166] Example 4 was repeated, except that sodium dodecyl sulfonate was replaced with sodium dodecyl sulfate.

[0167] The test results were similar to those of Example 3.

[0168] Example 11

[0169] Repeat Example 3, except that 2000 mL of water is replaced with 400 mL of water.

[0170] The test results were similar to those of Example 3.

[0171] Example 12

[0172] Repeat Example 4, except that 2000 mL of water is replaced with 400 mL of water.

[0173] The test results were similar to those of Example 4.

[0174] Comparative Example 1

[0175] Repeat Example 1, except that in step 1), alkali lignin is replaced with enzymatically hydrolyzed lignin.

[0176] Tests revealed that the enzymatically hydrolyzed lignin nanoparticles had a relatively large particle size (>40nm). This is because the preparation process of enzymatically hydrolyzed lignin differs from that of alkali lignin, resulting in a larger molecular weight and thus a larger size of the lignin nanoparticles.

[0177] Comparative Example 2

[0178] Repeat Example 1, except that the 0.07 mol / L hydrochloric acid solution in step 2) is changed to 0.02 mol / L.

[0179] Figure 9 and Figure 10 The images show scanning electron microscopy (SEM) images and particle size distribution diagrams of the alkali lignin nanoparticles obtained in Comparative Example 2. Testing revealed that the alkali lignin nanoparticles exhibited good stability (no aggregation after 180 days of storage), but the particle size distribution was wide (PDI > 0.2), with an average particle size of 30 nm. This was attributed to the low hydrochloric acid concentration, resulting in incomplete precipitation.

[0180] Comparative Example 3

[0181] Repeat Example 1, except that sodium lignosulfonate in step 1) is replaced with sodium dodecyl sulfate.

[0182] Testing revealed that the alkali lignin nanoparticles in the product exhibited poor stability (aggregating after 7 days of storage). This is because sodium dodecyl sulfate is difficult to stabilize in low pH environments, thus losing its function in modifying lignin nanoparticles.

[0183] Comparative Example 4

[0184] Example 1 was repeated, except that the reaction was carried out in a beaker instead of in a high-gravity rotating packed bed.

[0185] Figure 11 This is a scanning electron microscope image of the alkali lignin nanoparticles obtained in Comparative Example 4. The reaction time was determined to be at least 30 minutes. The alkali lignin nanoparticles exhibited poor stability (no aggregation after 7 days of storage), a wide particle size distribution (PDI > 0.2), and a particle size of 60 nm.

[0186] Comparative Example 5

[0187] Repeat Example 2, except that in step 1), alkali lignin is replaced with enzymatically hydrolyzed lignin.

[0188] Tests revealed that the enzymatically hydrolyzed lignin nanoparticles had a relatively large particle size (>80nm). This is because the preparation process of enzymatically hydrolyzed lignin differs from that of alkali lignin, resulting in a larger molecular weight and thus a larger size of the lignin nanoparticles.

[0189] Comparative Example 6

[0190] Repeat Example 2, except that the 0.07 mol / L hydrochloric acid solution in step 2) is changed to 0.02 mol / L.

[0191] Testing revealed that the alkali lignin nanoparticles exhibited good stability (no aggregation observed after 180 days of storage), but the particle size distribution was wide (PDI > 0.2), with an average particle size of 100 nm. This was attributed to the excessively low hydrochloric acid concentration, resulting in incomplete precipitation.

[0192] Comparative Example 7

[0193] Repeat Example 2, except that sodium lignosulfonate in step 1) is replaced with sodium dodecyl sulfate.

[0194] Testing revealed that the alkali lignin nanoparticles in the product exhibited poor stability (aggregating after 7 days of storage). This is because sodium dodecyl sulfate is difficult to stabilize in low pH environments, thus losing its function in modifying lignin nanoparticles.

[0195] Comparative Example 8

[0196] Example 2 was repeated, except that the reaction was carried out in a beaker instead of in a high-gravity rotating packed bed.

[0197] Testing revealed that the reaction time required was at least 30 minutes, and the product's alkali lignin nanoparticles exhibited poor stability (no agglomeration after 7 days of storage), a wide particle size distribution (PDI > 0.2), and a particle size of 90 nm.

[0198] Comparative Example 9

[0199] Example 3 was repeated, except that sodium dodecyl sulfonate was replaced with dodecyltrimethylammonium bromide.

[0200] Testing revealed that the product's alkali lignin nanoparticles exhibited severe agglomeration (PDI > 0.2) and poor stability (agglomeration occurred after 3 days of storage).

[0201] Comparative Example 10

[0202] Example 4 was repeated, except that sodium dodecyl sulfonate was replaced with dodecyltrimethylammonium bromide.

[0203] Testing revealed that the product's alkali lignin nanoparticles exhibited severe agglomeration (PDI > 0.2) and poor stability (agglomeration occurred after 3 days of storage).

[0204] Comparative Example 11

[0205] Example 3 was repeated, except that the aqueous acetone solution was replaced with N,N-dimethylformamide.

[0206] Tests revealed that no alkali lignin nanoparticles were obtained.

[0207] Comparative Example 12

[0208] Example 4 was repeated, except that the aqueous acetone solution was replaced with N,N-dimethylformamide.

[0209] Tests revealed that no alkali lignin nanoparticles were obtained.

[0210] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is impossible to exhaustively list all embodiments here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A method for preparing a liquid dispersion of lignin nanoparticles, characterized in that, Includes the following steps: 1) Add lignin to a good solvent, stir to dissolve, and form solution A; or add lignin and surfactant to a good solvent, stir to dissolve, and form solution A; 2) Add the surfactant to the unsuitable solvent, stir to dissolve, and form solution B; or use the unsuitable solvent as solution B; 3) Feed solution A and feed solution B are fed into a high-gravity rotating packed bed through a peristaltic pump, and after precipitation, a lignin nanoparticle suspension is obtained. 4) Centrifuge and wash the lignin nanoparticle suspension, and disperse it in a liquid to obtain a liquid dispersion of lignin nanoparticles. Alternatively, the lignin nanoparticle suspension can be rotary evaporated to obtain a liquid dispersion of lignin nanoparticles.

2. The method for preparing the lignin nanoparticle liquid dispersion according to claim 1, characterized in that: In step 1), the lignin is one of alkali lignin, enzymatically hydrolyzed lignin, sulfate lignin, organic solvent lignin, and lignin sulfonate; preferably, the lignin is one of alkali lignin and enzymatically hydrolyzed lignin; more preferably, the lignin is alkali lignin. Preferably, in step 1), the good solvent is selected from one or more of the following substances: water, aqueous sodium hydroxide solution, methanol, ethanol, ethylene glycol, N,N-dimethylformamide, acetone, tetrahydrofuran, γ-valerol, dimethyl sulfoxide, dichloromethane, and glycerol; preferably, the good solvent is one or more of water, aqueous sodium hydroxide solution, acetone, and γ-valerol; more preferably, the good solvent is water or aqueous sodium hydroxide solution. Preferably, in step 1), the stirring temperature is 10–80°C, and the stirring time is 5–60 min; Preferably, in step 1), the concentration of lignin in the liquid A is 1 to 120 g / L.

3. The method for preparing the lignin nanoparticle liquid dispersion according to claim 1, characterized in that: In step 1) or step 2), the surfactant is selected from one or more of the following substances: lignin sulfonate, sodium dodecyl sulfonate, sodium dodecyl sulfate, polyethylene glycol, polyvinylpyrrolidone, hydroxypropyl methylcellulose, dodecyltrimethylammonium bromide, cyclodextrin, mannitol, γ-aminopropyltriethoxysilane, γ-methacryloyloxypropyltrimethoxysilane; preferably, the surfactant is one or more of lignin sulfonate, sodium dodecyl sulfonate, polyvinylpyrrolidone, and sodium dodecyl sulfate; more preferably, the surfactant is lignin sulfonate; Preferably, in step 1) or step 2), the amount of surfactant used is 0-20% of the mass of lignin.

4. The method for preparing the lignin nanoparticle liquid dispersion according to claim 1, characterized in that: In step 2), the unsuitable solvent is selected from one or more of the following substances: 0.01–2.5 mol / L hydrochloric acid solution, 0.01–2.5 mol / L sulfuric acid solution, 0.01–2.5 mol / L acetic acid, 0.01–2.5 mol / L phosphoric acid, 0.01–2.5 mol / L oxalic acid, water, methanol, ethanol, isopropanol, and glycerol; more preferably, the unsuitable solvent is one or more of 0.01–2.5 mol / L hydrochloric acid solution, 0.01–2.5 mol / L sulfuric acid solution, and water; even more preferably, the unsuitable solvent is 0.01–2.5 mol / L hydrochloric acid solution. Preferably, in step 2), the stirring temperature is 10–80°C and the stirring time is 5–60 min.

5. The method for preparing the lignin nanoparticle liquid dispersion according to claim 1, characterized in that: In step 3), the reaction temperature inside the supergravity rotating packed bed is 10–90°C; more preferably, the temperature is 10–60°C. Preferably, in step 3), the feed flow rate of liquid A is 20-800 mL / min, and the feed flow rate of liquid B is 200-2000 mL / min; Preferably, in step 3), the ratio of feed flow rates of liquid A to liquid B is 1:1 to 1:40; Preferably, in step 3), the rotor speed of the supergravity rotating filling bed is 300 to 3000 rpm; Preferably, in step 4), the centrifugation speed is 6000–12000 rpm; the centrifugation time is 3–15 min. Preferably, in step 4), the solvent used for washing is selected from one or more of the following substances: water, acid solution with pH = 2 to 5, methanol, ethanol, glycerol, isopropanol, acetone, and ethyl acetate; Preferably, in step 4), the liquid is selected from one or more of the following substances: water, an acid solution with pH = 2 to 5, methanol, ethanol, isopropanol, acetone, and ethyl acetate; preferably, the liquid is one or more of water, an acid solution with pH = 2 to 5, methanol, and ethanol; more preferably, the liquid is an acid solution with pH = 2 to 5. Preferably, in step 4), the temperature of the rotary evaporator is 25–85°C and the rotation speed is 10–80 rpm.

6. A method for preparing a lignin nanoparticle solid dispersion, characterized in that, Includes the following steps: 11) Add lignin to a good solvent, stir to dissolve, and form solution A; or add lignin and surfactant to a good solvent, stir to dissolve, and form solution A; 12) Add the surfactant to the unsuitable solvent, stir to dissolve, and form solution B; or use the unsuitable solvent as solution B; 13) Feed solution A and feed solution B are fed into a high-gravity rotating packed bed through a peristaltic pump, and after precipitation, a lignin nanoparticle suspension is obtained. 14) The lignin nanoparticle suspension is passed into a spray dryer for spray drying to obtain the corresponding solid dispersion; or the lignin nanoparticle suspension is centrifuged, washed, and the wet solid is vacuum dried to obtain the lignin nanoparticle solid dispersion.

7. The method for preparing the lignin nanoparticle solid dispersion according to claim 6, characterized in that: In step 11), the lignin is one of alkali lignin, enzymatically hydrolyzed lignin, sulfate lignin, organic solvent lignin, and lignin sulfonate; preferably, the lignin is one of alkali lignin and enzymatically hydrolyzed lignin; more preferably, the lignin is alkali lignin. Preferably, in step 11), the good solvent is selected from one or more of the following substances: water, aqueous sodium hydroxide solution, methanol, ethanol, ethylene glycol, N,N-dimethylformamide, acetone, tetrahydrofuran, γ-valerolactone, dimethyl sulfoxide, dichloromethane, and glycerol; preferably, the good solvent is one or more of water, aqueous sodium hydroxide solution, acetone, and γ-valerolactone; more preferably, the good solvent is water or aqueous sodium hydroxide solution. Preferably, in step 11), the stirring temperature is 10–80°C, and the stirring time is 5–60 min; Preferably, in step 11), the concentration of lignin in the liquid A is 1 to 120 g / L.

8. The method for preparing the lignin nanoparticle solid dispersion according to claim 6, characterized in that: In step 11) or step 12), the surfactant is selected from one or more of the following substances: sodium dodecyl sulfonate, sodium dodecyl sulfate, polyethylene glycol, polyvinylpyrrolidone, hydroxypropyl methylcellulose, dodecyltrimethylammonium bromide, cyclodextrin, mannitol, γ-aminopropyltriethoxysilane, and γ-methacryloyloxypropyltrimethoxysilane; preferably, the surfactant is one or more of lignin sulfonate, sodium dodecyl sulfonate, polyvinylpyrrolidone, and sodium dodecyl sulfate; more preferably, the surfactant is lignin sulfonate; Preferably, in step 11) or step 12), the amount of surfactant used is 0-20% of the mass of lignin; Preferably, in step 12), the unsuitable solvent is selected from one or more of the following substances: 0.01–2.5 mol / L hydrochloric acid solution, 0.01–2.5 mol / L sulfuric acid solution, 0.01–2.5 mol / L acetic acid, 0.01–2.5 mol / L phosphoric acid, 0.01–2.5 mol / L oxalic acid, water, methanol, ethanol, isopropanol, and glycerol; more preferably, the unsuitable solvent is one or more of 0.01–2.5 mol / L hydrochloric acid solution, 0.01–2.5 mol / L sulfuric acid solution, and water; even more preferably, the unsuitable solvent is 0.01–2.5 mol / L hydrochloric acid solution. Preferably, in step 12), the stirring temperature is 10–80°C and the stirring time is 5–60 min.

9. The method for preparing the lignin nanoparticle solid dispersion according to claim 6, characterized in that: In step 13), the reaction temperature inside the supergravity rotating packed bed is 10–90°C; more preferably, the temperature is 10–60°C. Preferably, in step 13), the feed flow rate of liquid A is 20-800 mL / min, and the feed flow rate of liquid B is 200-2000 mL / min; Preferably, in step 13), the ratio of the feed flow rates of liquid A to liquid B is 1:1 to 1:40; Preferably, in step 13), the rotor speed of the supergravity rotating filling bed is 300 to 3000 rpm.

10. The method for preparing the lignin nanoparticle solid dispersion according to claim 6, characterized in that: In step 14), the centrifugation speed is 6000-12000 rpm; the centrifugation time is 3-15 min. Preferably, in step 14), the solvent used for washing is selected from one or more of the following substances: water, acid solution with pH = 2 to 5, methanol, ethanol, glycerol, isopropanol, acetone, and ethyl acetate; Preferably, in step 14), the liquid is selected from one or more of the following substances: water, an acid solution with pH = 2 to 5, methanol, ethanol, isopropanol, acetone, and ethyl acetate; preferably, the liquid is one or more of water, an acid solution with pH = 2 to 5, methanol, and ethanol; more preferably, the liquid is an acid solution with pH = 2 to 5. Preferably, in step 14), the temperature of the rotary evaporation is 25-85°C and the rotation speed is 10-80 rpm.

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