A solvent-enhanced agricultural and forestry biomass separation and in-situ lignin nanosphere / bottle self-assembly method

Abstract

The present invention discloses a method for enhancing the separation of agricultural and forestry biomass by using a solvent co-enhancing agent and for self-assembling lignin nanospheres / bottles in situ, and belongs to the technical field of biomass refining and preparation of degradable polymer nanomaterials. The present invention provides a new CELF method for separating agricultural and forestry biomass, and uses a solvent system composed of tetrahydrofuran and an aqueous sodium carbonate solution to preferentially solvate hemicellulose and lignin, components of agricultural and forestry biomass, under mild conditions, to efficiently separate components of lignocellulosic biomass; and then self-assembles the lignin-containing solution in situ into lignin micro-nanospheres / bottles, and finally realizes separation and micro-nano integration. The lignin nanospheres / bottles prepared by the present invention make the process of preparing lignin nanospheres / bottles simple and energy-efficient, and there is no need to separate lignin solids.

Description

Technical Field

[0001] The invention belongs to the technical field of biomass refining and preparation of degradable polymer nanomaterials, and specifically relates to a solvent-assisted enhanced agricultural and forestry biomass separation and in-situ lignin nanosphere / bottle self-assembly method. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] The abundant agricultural and forestry biomass on the earth can be prepared into renewable fuels, chemicals and materials through a series of means and methods, reducing the dependence and utilization of non-renewable petrochemical resources, which is of great significance for promoting the realization of carbon reduction goals. The main carbon-containing components of agricultural and forestry biomass include cellulose, lignin and hemicellulose. Current biorefining methods cannot effectively and highly utilize these three components, resulting in a huge waste of resources. If both lignin and carbohydrates can be fully utilized to produce high value-added or bulk products, it will have far-reaching significance for improving the overall economy of the biomass refining industry and implementing carbon neutrality goals.

[0004] Various pretreatment techniques, such as hot water, dilute acid, alkali, ammonia fiber explosion, deep eutectic solvents, ionic liquids, and / or their combination pretreatments have been used to enhance the deconstruction of agroforestry biomass or bioconversion of biomass sugars. Recently, a promising fractionation pretreatment method, called cosolvent enhanced fractionation of agroforestry biomass (CELF), has been developed through intensive multiscale analysis of solvent-lignin, solvent-hemicellulose, and solvent-cellulose interactions to better solvate lignin-carbohydrate complexes at milder temperatures. All previous CELFs used a single-phase cosolvent mixture of tetrahydrofuran aqueous solution and dilute acid as catalysts to achieve preferential solvation of lignin or cellulose by simply adjusting the reaction parameters. CELF is an effective solvolysis pretreatment that enhances the deconstruction and fractionation of recalcitrant lignocellulosic biomass and produces high-purity lignin and carbohydrates, which are beneficial for further conversion. For CELF, there are no articles or patent reports that use a single-phase cosolvent mixture of tetrahydrofuran aqueous solution and a strong base and weak acid salt as catalysts to achieve preferential solvation of lignin or cellulose.

[0005] In addition, an effective way to utilize lignin for high added value is to process lignin into micro-nano form. In recent years, there have been many reports on the micro-nano self-assembly of lignin, but most of them are obtained by dissolving solid lignin powder obtained from biorefining or industrial lignin powder in a certain solvent through certain means. However, there are no reports on the integration of biomass component separation and lignin micro-nano sphere / bottle self-assembly. Summary of the invention

[0006] In order to solve the deficiencies of the prior art, the purpose of the present invention is to provide a method for solvent-enhanced separation of agricultural and forestry biomass and in-situ self-assembly of lignin nanospheres / bottles. The present invention provides a new CELF method for separation of agricultural and forestry biomass, using a solvent system composed of tetrahydrofuran and sodium carbonate aqueous solution to preferentially solvate hemicellulose and lignin components of agricultural and forestry biomass under mild conditions, and efficiently separate the components of lignocellulosic biomass; then the lignin-containing solution is self-assembled in-situ into lignin micro-nanospheres / bottles, and finally separation and micro-nano integration are achieved.

[0007] In order to achieve the above object, the technical solution of the present invention is:

[0008] In one aspect, the present invention provides a method for solvent-assisted separation of agricultural and forestry biomass and in-situ lignin nanosphere / bottle self-assembly, comprising the following steps:

[0009] The biomass raw material is reacted in a solution system consisting of tetrahydrofuran, sodium carbonate and water, and the solid and liquid are separated. The filtrate contains lignin. The pH of the filtrate is adjusted, and water is added to adjust the ratio of water and tetrahydrofuran in the filtrate, so that the lignin is self-assembled in situ in the filtrate to form lignin nanospheres / bottles.

[0010] The present invention develops a simple and green component separation coupled lignin in situ self-assembly method, which realizes the efficient preparation and structural morphology regulation of nanospheres / bottles by utilizing harmless, biocompatible and low-cost lignin, which is not only of great significance for further expanding the scope of lignin utilization, but also greatly broadens the space for lignin in practical applications.

[0011] The specific process is as follows: the biomass raw material is mechanically crushed and sieved for standby use (20-60 mesh), the biomass powder is taken into the reactor, 0-0.2 g of Na2CO3 and a certain proportion of distilled water and tetrahydrofuran are added, and the reaction is carried out in a high-temperature and high-pressure reactor, the temperature is controlled within 100-160°C, and the reaction time is controlled within 0.1-5 h. After the reaction is completed, the reaction is taken out and cooled, filtered and separated with a Buchner funnel, and washed 1-3 times with a tetrahydrofuran aqueous solution of the same proportion to complete the solid-liquid separation. A slurry rich in cellulose and hemicellulose components and a filtrate containing lignin are obtained. The volume of the added liquid is recorded. The pH value of the filtrate after the reaction is measured and adjusted to neutral with a 0.2 mol / L hydrochloric acid solution. Then, distilled water is added dropwise with a constant flow pump to adjust the ratio of distilled water and tetrahydrofuran in the filtrate to 7:3. The speed during the distilled water adjustment process is 50-300 r / min. The tetrahydrofuran in the filtrate is recovered by rotary evaporation, and finally a solution containing lignin micro-nanospheres / bottles is obtained, thereby realizing in-situ self-assembly to form lignin nanospheres / bottles.

[0012] In one or more embodiments, the biomass raw material is various agricultural and forestry biomass resources such as corn cob residues, wheat straw, straw, eucalyptus, pine wood or corn cobs.

[0013] In one or more embodiments, the biomass raw material needs to be pre-treated by mechanical crushing before use, and sieved to obtain 20-60 mesh biomass powder for later use.

[0014] In one or more embodiments, the ratio of biomass feedstock, sodium carbonate, tetrahydrofuran and water is, in g / g / mL / mL, 1:(0-0.2):(10-20):(5-10), preferably 1:(0.1-0.2):(10-15):(5-10).

[0015] In one or more embodiments, the reaction temperature is 100-160°C, and the reaction time is 0.5-5h. Preferably, the reaction temperature is 120-140°C, more preferably 140°C, and the reaction time is 0.5-2h.

[0016] In one or more embodiments, the pH of the filtrate is adjusted by using an acid solution to adjust the pH to neutral.

[0017] In one or more embodiments, the ratio of water to tetrahydrofuran is adjusted to (7:3)-(9:1), preferably (7:3):(8:2).

[0018] In one or more embodiments, during the process of adjusting the ratio of water to tetrahydrofuran, the stirring rate of the filtrate is 50-300 r / min.

[0019] In a second aspect, the present invention provides a lignin nanosphere / bottle prepared by the above method. The lignin nanosphere / bottle has a uniform morphology, an average particle size of 100-500 nm, preferably 100-250 nm, and more preferably 100-150 nm; and an average pore size of 20-200 nm, preferably 30-160 nm, and more preferably 30-55 nm.

[0020] In a third aspect, the present invention provides an application of lignin nanospheres / bottles in nanocarriers.

[0021] The beneficial effects of the present invention are:

[0022] (1) The present invention uses a co-solvent (sodium carbonate, tetrahydrofuran) to enhance lignocellulose fractionation, which is an advanced pretreatment technology that can remove most of the lignin from the biomass, and uses the liquid after the reaction to prepare lignin nanospheres / bottles in situ, making the process of preparing lignin nanospheres / bottles simple and energy-saving, without the need to separate lignin solids.

[0023] (2) The miscible mixture of tetrahydrofuran and weakly alkaline aqueous sodium carbonate used in the present invention can preferentially solvate lignin, thereby making it easy to remove it from cellulose and preventing lignin from self-aggregation and redeposition.

[0024] (3) The tetrahydrofuran used in the present invention is a renewable solvent that can be sustainably produced from lignocellulosic biomass, which has low cost, strong solubility and simple recovery process.

[0025] (4) The in situ prepared lignin nanospheres / bottles of the present invention have a small particle size, with an average particle size of 100-500 nm, and an average pore size of 20-200 nm, which is more conducive to subsequent applications in nanocarriers, such as drug loading, controlled release, antibacterial, and anti-ultraviolet. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0027] Figure 1 This is the SEM morphology of the lignin nanobottle obtained in situ in Example 3 of the present invention;

[0028] Figure 2 This is the SEM morphology of the lignin nanobottle obtained in situ in Example 4 of the present invention;

[0029] Figure 3 This is the SEM morphology of the lignin nanobottle obtained in situ in Example 5 of the present invention;

[0030] Figure 4 This is a SEM morphology of the lignin nanospheres obtained in situ in Example 7 of the present invention;

[0031] Figure 5 This is a SEM morphology of the lignin obtained in situ in Comparative Example 3 of the present invention;

[0032] Figure 6 This is an infrared image of the lignin nanobottle obtained in situ in Example 4 of the present invention. DETAILED DESCRIPTION

[0033] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in conjunction with specific embodiments.

[0034] Example 1

[0035] Take 1 g corncob residue powder (40 mesh) and place it in a reaction bottle, add 6 mL of distilled water and 14 mL of tetrahydrofuran, put it in a reactor and react at 140 °C and 400 r / min for 1 h. After the reaction is completed, take it out and cool it down, filter it with a Buchner funnel, and wash it three times with the same proportion of water and tetrahydrofuran. Solid-liquid separation, obtain a filter residue rich in cellulose and hemicellulose components and a filtrate containing lignin. Record the volume of the added liquid for standby use. Then use 0.2 mol / L hydrochloric acid to adjust the filtrate to neutral. After that, use a constant flow pump to continuously add distilled water to accurately adjust the ratio of distilled water to tetrahydrofuran in the filtrate to 7:3, thereby successfully preparing a lignin nanobottle. In the process of adjusting the ratio of distilled water to tetrahydrofuran in the filtrate by distilled water, the speed of the filtrate must be kept constant at 300 r / min. Finally, the tetrahydrofuran in the filtrate is recovered by rotary evaporation.

[0036] Example 2

[0037] 1 g corncob residue powder (40 mesh) was placed in a reaction bottle, 0.05 g sodium carbonate was added, and 6 mL of distilled water and 14 mL of tetrahydrofuran were added. The mixture was placed in a reactor and reacted at 140 °C and 400 r / min for 1 h. After the reaction was completed, the mixture was cooled down, filtered with a Buchner funnel, and washed three times with the same proportion of water and tetrahydrofuran. The solid-liquid separation was performed to obtain a filtrate rich in cellulose and hemicellulose components and a filtrate containing lignin. The volume of the added liquid was recorded and set aside. The filtrate was then adjusted to neutral using 0.2 mol / L hydrochloric acid. After that, a constant flow pump was used to continuously add distilled water to accurately adjust the ratio of distilled water to tetrahydrofuran in the filtrate to 7:3, thereby successfully preparing a lignin nanobottle. In the process of adjusting the ratio of distilled water to tetrahydrofuran in the filtrate by distilled water, the rotation speed of the filtrate should be kept constant at 300 r / min. Finally, the tetrahydrofuran in the filtrate was recovered by rotary evaporation.

[0038] Example 3

[0039] 1 g corncob residue powder (40 mesh) was placed in a reaction bottle, 0.1 g sodium carbonate, 6 mL distilled water and 14 mL tetrahydrofuran were added, and the mixture was placed in a reactor and reacted at 140 °C and 400 r / min for 1 h. After the reaction was completed, the mixture was taken out and cooled, filtered with a Buchner funnel, and washed three times with the same proportion of water and tetrahydrofuran. Solid-liquid separation was performed to obtain a filtrate rich in cellulose and hemicellulose components and a filtrate containing lignin. The volume of the added liquid was recorded and set aside. The filtrate was then adjusted to neutral using 0.2 mol / L hydrochloric acid. After that, a constant flow pump was used to continuously drip distilled water to accurately adjust the ratio of distilled water to tetrahydrofuran in the filtrate to 7:3, thereby successfully preparing a lignin nanobottle. In the process of adjusting the ratio of distilled water to tetrahydrofuran in the filtrate by distilled water, the rotation speed of the filtrate should be kept constant at 300 r / min. Finally, the tetrahydrofuran in the filtrate was recovered by rotary evaporation.

[0040] Example 4

[0041] 1 g corncob residue powder (40 mesh) was placed in a reaction bottle, 0.2 g sodium carbonate, 6 mL distilled water and 14 mL tetrahydrofuran were added, and the mixture was placed in a reactor and reacted at 140 °C and 400 r / min for 1 h. After the reaction was completed, the mixture was taken out and cooled, filtered with a Buchner funnel, and washed three times with the same proportion of water and tetrahydrofuran. Solid-liquid separation was performed to obtain a filtrate rich in cellulose and hemicellulose components and a filtrate containing lignin. The volume of the added liquid was recorded and set aside. Then, the filtrate was adjusted to neutrality using 0.2 mol / L hydrochloric acid. After that, a constant flow pump was used to continuously drip distilled water to accurately adjust the ratio of distilled water to tetrahydrofuran in the filtrate to 7:3, thereby successfully preparing a lignin nanobottle. In the process of adjusting the ratio of distilled water to tetrahydrofuran in the filtrate by distilled water, the rotation speed of the filtrate should be kept constant at 300 r / min. Finally, the tetrahydrofuran in the filtrate was recovered by rotary evaporation.

[0042] Example 5

[0043] 1 g corncob powder (40 mesh) was placed in a reaction bottle, 0.2 g sodium carbonate, 6 mL distilled water and 14 mL tetrahydrofuran were added, and the mixture was placed in a reactor and reacted at 140 °C and 400 r / min for 1 h. After the reaction was completed, the mixture was cooled down, filtered with a Buchner funnel, and washed three times with the same proportion of water and tetrahydrofuran. The solid-liquid separation was performed to obtain a filtrate rich in cellulose and hemicellulose components and a filtrate containing lignin. The volume of the added liquid was recorded. The filtrate was then adjusted to neutral using 0.2 mol / L hydrochloric acid. After that, a constant flow pump was used to continuously drip distilled water to accurately adjust the ratio of distilled water to tetrahydrofuran in the filtrate to 7:3, thereby successfully preparing a lignin nanobottle. In the process of adjusting the ratio of distilled water to tetrahydrofuran in the filtrate by distilled water, the rotation speed of the filtrate should be kept constant at 300 r / min. Finally, the tetrahydrofuran in the filtrate was recovered by rotary evaporation.

[0044] Example 6

[0045] Take 1 g of straw (40 mesh) and place it in a reaction bottle, add 0.2 g of sodium carbonate, 6 mL of distilled water and 14 mL of tetrahydrofuran, put it in a reactor and react at 140 °C and 400 r / min for 1 h. After the reaction is completed, take it out and cool it down, filter it with a Buchner funnel, and wash it three times with the same proportion of water and tetrahydrofuran. Solid-liquid separation, obtain a residue rich in cellulose and hemicellulose components and a filtrate containing lignin. Record the volume of the added liquid for standby use. Then use 0.2 mol / L hydrochloric acid to adjust the filtrate to neutral. After that, use a constant flow pump to continuously add distilled water to accurately adjust the ratio of distilled water to tetrahydrofuran in the filtrate to 7:3, thereby successfully preparing lignin nanospheres. In the process of adjusting the ratio of distilled water to tetrahydrofuran in the filtrate by distilled water, the speed of the filtrate must be kept constant at 300 r / min. Finally, the tetrahydrofuran in the filtrate is recovered by rotary evaporation.

[0046] Example 7

[0047] Take 1 g of eucalyptus powder (40 mesh) and place it in a reaction bottle, add 0.2 g of sodium carbonate, 6 mL of distilled water and 14 mL of tetrahydrofuran, put it in a reactor and react at 140 °C and 400 r / min for 1 h. After the reaction is completed, take it out and cool it down, filter it with a Buchner funnel, and wash it three times with the same proportion of water and tetrahydrofuran. Solid-liquid separation, obtain a residue rich in cellulose and hemicellulose components and a filtrate containing lignin. Record the volume of the added liquid for standby use. Then use 0.2 mol / L hydrochloric acid to adjust the filtrate to neutral. After that, use a constant flow pump to continuously add distilled water to accurately adjust the ratio of distilled water to tetrahydrofuran in the filtrate to 7:3, thereby successfully preparing lignin nanospheres. In the process of adjusting the ratio of distilled water to tetrahydrofuran in the filtrate by distilled water, the speed of the filtrate must be kept constant at 300 r / min. Finally, the tetrahydrofuran in the filtrate is recovered by rotary evaporation.

[0048] Example 8

[0049] Take 1 g of pine powder (40 mesh) and place it in a reaction bottle, add 0.2 g of sodium carbonate, 6 mL of distilled water and 14 mL of tetrahydrofuran, put it in a reactor and react at 140 °C and 400 r / min for 1 h. After the reaction is completed, take it out and cool it down, filter it with a Buchner funnel, and wash it three times with the same proportion of water and tetrahydrofuran. Solid-liquid separation, obtain a filtrate rich in cellulose and hemicellulose components and a filtrate containing lignin. Record the volume of the added liquid for standby use. Then use 0.2 mol / L hydrochloric acid to adjust the filtrate to neutral. After that, use a constant flow pump to continuously add distilled water to accurately adjust the ratio of distilled water to tetrahydrofuran in the filtrate to 7:3, thereby successfully preparing lignin nanospheres. In the process of adjusting the ratio of distilled water to tetrahydrofuran in the filtrate by distilled water, the speed of the filtrate must be kept constant at 300 r / min. Finally, the tetrahydrofuran in the filtrate is recovered by rotary evaporation.

[0050] Example 9

[0051] 1 g of bamboo powder (40 mesh) was placed in a reaction bottle, 0.2 g of sodium carbonate, 6 mL of distilled water and 14 mL of tetrahydrofuran were added, and the mixture was placed in a reactor and reacted at 140 °C and 400 r / min for 1 h. After the reaction was completed, the mixture was taken out and cooled, filtered with a Buchner funnel, and washed three times with the same proportion of water and tetrahydrofuran. The solid-liquid separation was performed to obtain a filtrate rich in cellulose and hemicellulose components and a filtrate containing lignin. The volume of the added liquid was recorded and set aside. Then, the filtrate was adjusted to neutrality using 0.2 mol / L hydrochloric acid. After that, a constant flow pump was used to continuously add distilled water to accurately adjust the ratio of distilled water to tetrahydrofuran in the filtrate to 7:3, thereby successfully preparing lignin nanospheres. In the process of adjusting the ratio of distilled water to tetrahydrofuran in the filtrate by distilled water, the rotation speed of the filtrate should be kept constant at 300 r / min. Finally, the tetrahydrofuran in the filtrate was recovered by rotary evaporation.

[0052] Example 10

[0053] 1 g corncob residue powder (40 mesh) was placed in a reaction bottle, 0.2 g sodium carbonate, 6 mL distilled water and 14 mL tetrahydrofuran were added, and the mixture was placed in a reactor and reacted at 120 °C and 400 r / min for 1 h. After the reaction was completed, the mixture was taken out and cooled, filtered with a Buchner funnel, and washed three times with the same proportion of water and tetrahydrofuran. The solid-liquid separation was performed to obtain a filtrate rich in cellulose and hemicellulose components and a filtrate containing lignin. The volume of the added liquid was recorded and set aside. The filtrate was then adjusted to neutral using 0.2 mol / L hydrochloric acid. After that, a constant flow pump was used to continuously drip distilled water to accurately adjust the ratio of distilled water to tetrahydrofuran in the filtrate to 7:3, thereby successfully preparing a lignin nanobottle. In the process of adjusting the ratio of distilled water to tetrahydrofuran in the filtrate by distilled water, the rotation speed of the filtrate should be kept constant at 300 r / min. Finally, the tetrahydrofuran in the filtrate was recovered by rotary evaporation.

[0054] Embodiment 11

[0055] Take 1 g corncob residue powder (40 mesh) and place it in a reaction bottle, add 0.2 g of sodium carbonate, 6 mL of distilled water and 14 mL of tetrahydrofuran, put it in a reactor and react at 140 °C and 400 r / min for 1 h. After the reaction is completed, take it out and cool it down, filter it with a Buchner funnel, and wash it three times with the same proportion of water and tetrahydrofuran. Solid-liquid separation, obtain a filter residue rich in cellulose and hemicellulose components and a filtrate containing lignin. Record the volume of the added liquid for later use. Then use 0.2 mol / L hydrochloric acid to adjust the filtrate to neutral. After that, use a constant flow pump to continuously add distilled water to accurately adjust the ratio of distilled water to tetrahydrofuran in the filtrate to 8:2, thereby successfully preparing a lignin nanobottle. In the process of adjusting the ratio of distilled water to tetrahydrofuran in the filtrate by distilled water, the speed of the filtrate must be kept constant at 300 r / min. Finally, the tetrahydrofuran in the filtrate is recovered by rotary evaporation.

[0056] Comparative Example 1 - Different solvent systems

[0057] Take 1 g corncob residue powder (40 mesh) and place it in a reaction bottle, add 0.2 g sodium carbonate, 6 mL distilled water and 14 mL ethanol, put it in a reactor and react for 1 h at 140 °C and 400 r / min. After the reaction is completed, take it out and cool it down, filter it with a Buchner funnel, and wash it three times with the same proportion of water and tetrahydrofuran. Solid-liquid separation, obtain the filter residue rich in cellulose and hemicellulose components and the filtrate containing lignin.

[0058] Comparative Example 2 - Different solvent systems

[0059] Take 1 g corncob residue powder (40 mesh) and place it in a reaction bottle, add 0.2 g sulfuric acid, 6 mL distilled water and 14 mL tetrahydrofuran, put it in a reactor and react for 1 h at 140 °C and 400 r / min. After the reaction is completed, take it out and cool it down, filter it with a Buchner funnel, and wash it three times with the same proportion of water and tetrahydrofuran. Solid-liquid separation, obtain the filter residue rich in cellulose and hemicellulose components and the filtrate containing lignin.

[0060] Comparative Example 3 - Different Ratios of Water to THF

[0061] Take 1 g corncob residue powder (40 mesh) and place it in a reaction bottle, add 0.2 g of sodium carbonate, 6 mL of distilled water and 14 mL of tetrahydrofuran, put it in a reactor and react at 140 °C and 400 r / min for 1 h. After the reaction is completed, take it out and cool it down, filter it with a Buchner funnel, and wash it three times with the same proportion of water and tetrahydrofuran. Solid-liquid separation, obtain a residue rich in cellulose and hemicellulose components and a filtrate containing lignin. Record the volume of the added liquid for later use. Then use 0.2 mol / L hydrochloric acid to adjust the filtrate to neutral. After that, use a constant flow pump to continuously add distilled water to accurately adjust the ratio of distilled water to tetrahydrofuran in the filtrate to 4:6. In the process of adjusting the ratio of distilled water to tetrahydrofuran in the filtrate by distilled water, the speed of the filtrate must be kept constant at 300 r / min. Finally, the tetrahydrofuran in the filtrate is recovered by rotary evaporation.

[0062] Table 1

[0063]

[0064] Table 1 shows the reaction solid recovery rate taking corncob residue as an example. It can be seen from Table 1 that the reaction solid recovery rate of the present invention under different Na2CO3 addition amounts in a mixed system of tetrahydrofuran and water is that when the Na2CO3 addition amount is 0.2 g, the solid recovery rate of the reaction is the lowest, that is, the lignin removal rate is the highest, and most of the lignin in the raw material enters the solvent system, which makes it easier to prepare lignin nanospheres / bottles. However, Comparative Example 1 obtained a solid recovery rate of up to 88% by adding 0.2 g of Na2CO3 to a mixed system of ethanol and water, that is, the delignification effect is extremely poor, which is not conducive to the in-situ preparation of lignin nanospheres / bottles. At the same time, Comparative Example 2 also obtained a solid recovery rate of up to 72% under the reaction conditions of adding 0.2 g H2SO4 to a mixed system of tetrahydrofuran and water, which is still not conducive to the in-situ preparation of lignin nanospheres / bottles.

[0065] Table 2

[0066]

[0067] Table 2 shows the concentration of low molecular weight products in the hydrolyzate at different Na2CO3 addition amounts. As shown in Table 2, the concentration of low molecular weight products in the hydrolyzate at different Na2CO3 addition amounts in the mixed system of tetrahydrofuran and water of the present invention increases with the increase of Na2CO3 addition amount, but the cellulose retention rate decreases. The lower cellulose retention rate is not conducive to the value-added application of biomass refining. Therefore, the addition amount of sodium carbonate is 0.2 g for the best.

[0068] Table 3

[0069]

[0070] Table 3 shows the solid recovery rate and the concentration of low molecular weight products in the hydrolyzate under the reaction conditions of 140°C, 1h, distilled water:tetrahydrofuran (v:v) of 7:3, and Na2CO3 addition of 0.2 g. As shown in Table 3, the solid recovery rate and the concentration of low molecular weight products in the hydrolyzate under the reaction conditions of 140°C, 1h, distilled water:tetrahydrofuran (v:v) of 7:3, and Na2CO3 addition of 0.2 g in the present invention can be seen that the use of mild co-solvent enhanced lignocellulose fractionation (CELF) pretreatment establishes an efficient and mild route that can be used for the fractionation and hydrolysis of different lignocellulosic biomass.

[0071] Figure 1 This is the SEM morphology of the in-situ obtained lignin nanobottle of Example 3. Figure 1 The results shown in the figure show that the present invention successfully achieved in-situ preparation under specific conditions, i.e., the temperature was set at 140 °C, the reaction time was 1 h, a mixed solvent of distilled water and tetrahydrofuran was used in a volume ratio of 7:3, and 0.1 g of Na2CO3 was added as a reaction aid, and a uniform morphology of lignin nanobottles was obtained. The average particle size was 379.8 nm, which was relatively large, and the average pore size was 152.8 nm.

[0072] Figure 2 This is the SEM morphology of the lignin nanobottle obtained in situ in Example 4. Figure 2 The results shown in the figure show that the present invention successfully achieved in-situ preparation under specific conditions, that is, the temperature was set to 140 ° C, the reaction time was 1 h, a mixed solvent of distilled water and tetrahydrofuran was used in a volume ratio of 7:3, and 0.2 g of Na2CO3 was added as a reaction aid, and a lignin nanobottle with uniform morphology was obtained. The average particle size of the lignin nanobottle obtained by the preparation method of Example 4 was 139.42 nm, and the average pore size was 50.8 nm.

[0073] Figure 3 This is the SEM morphology of the lignin nanobottle obtained in situ in Example 5. Figure 3 The results shown in the figure show that the present invention successfully achieved in-situ preparation under specific conditions, that is, the temperature was set to 140°C, the reaction time was 1 h, a mixed solvent of distilled water and tetrahydrofuran was used in a volume ratio of 7:3, and 0.2 g of Na2CO3 was added as a reaction aid, and a lignin nanobottle with uniform morphology was obtained. The lignin nanobottle obtained by the preparation method of Example 5 had an average particle size of 116.49 nm and an average pore size of 38.8 nm.

[0074] Figure 4This is the SEM morphology of the lignin nanospheres obtained in situ in Example 7. Figure 4 The results shown in the figure show that the present invention successfully achieved in-situ preparation under specific conditions, that is, the temperature was set to 140°C, the reaction time was 1 h, a mixed solvent of distilled water and tetrahydrofuran was used in a volume ratio of 7:3, and 0.2 g of Na2CO3 was added as a reaction aid, and lignin nanospheres with uniform morphology were obtained. The average particle size of the lignin nanospheres obtained by the preparation method of Example 7 was 207.74 nm.

[0075] Figure 5 This is the SEM morphology of the lignin nanospheres obtained in situ in Comparative Example 3. Figure 5 The results shown show that the preparation method of Comparative Example 3 did not achieve in-situ preparation of lignin nanospheres / bottles.

[0076] Figure 6 This is the infrared spectrum of the lignin nanobottle obtained in situ in Example 4. Figure 6 The results shown are the infrared structure of the composite lignin.

[0077] In addition, it should be noted that the preparation method of the present application can be used to prepare lignin nanospheres / bottles, but whether lignin nanospheres or lignin nanobottles are prepared depends on the different biomass raw materials. Due to the rigid structure of corn stalks and corn cobs, lignin cannot form a dense structure, and finally forms a lignin nanobottle structure. The remaining raw material lignin contains more flexible structures that are easy to form a dense structure, thus forming lignin nanospheres.

[0078] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for solvent-enhanced separation of agricultural and forestry biomass and in-situ lignin nanosphere / bottle self-assembly, characterized in that: The following steps are involved: The biomass raw material is reacted in a solution system consisting of tetrahydrofuran, sodium carbonate and water, and the solid and liquid are separated. The filtrate contains lignin. The pH of the filtrate is adjusted, and water is added to adjust the ratio of water and tetrahydrofuran in the filtrate, so that the lignin is self-assembled in situ in the filtrate to form lignin nanospheres / bottles; The biomass raw material is one of corn cob residue, wheat straw, straw, eucalyptus, pine wood or corn cob; When the biomass raw material is corn cob residue or corn cob, nanobottles can be formed; When the biomass raw material is wheat straw, stalks, eucalyptus or pine, nanospheres can be formed; Adjust the ratio of water to tetrahydrofuran to (7:3) - (9:1); The pH of the filtrate is adjusted to neutral using an acid solution; The lignin nanospheres / bottles have uniform morphology and an average particle size of 100-500 nm; The ratio of biomass raw material, sodium carbonate, tetrahydrofuran and water is, in terms of g / g / mL / mL, 1:(0.1-0.2):(10-20):(5-10).

2. The method according to claim 1, characterized in that: The biomass raw material is mechanically crushed and pre-treated before use, and sieved to obtain 20-60 mesh biomass powder.

3. The method according to claim 1, characterized in that The reaction temperature is 100-160°C; the reaction time is 0.5-5h.

4. The method according to claim 3, characterized in that The reaction temperature is 120-140°C; the reaction time is 0.5-2h.

5. The method according to claim 1, characterized in that During the process of adjusting the ratio of water to tetrahydrofuran, the stirring rate of the filtrate was 50-300 r / min.

6. A lignin nanobottle prepared by the method according to any one of claims 1 to 5.

7. The lignin nanobottle according to claim 6, characterized in that: The average pore size of the lignin nanobottle is 20-200 nm.

8. Use of the lignin nanobottle according to claim 6 or 7 in the preparation of nanocarriers.

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