Method for efficiently separating and synchronously preparing furfural from lignocellulose mediated by temperature control type phase change system

Abstract

The invention discloses a method for synchronously preparing furfural by efficiently separating lignocellulose mediated by a temperature control type phase change system. The method comprises the following steps: washing, drying and crushing agricultural wastes to obtain a material; placing the crushed material and a micromolecular diol-salt two-phase system in a reaction kettle, sealing, heating, cooling after heating, performing suction filtration and separation on the material to obtain filtrate and solid residues, performing phase separation on the filtrate, and collecting an upper-layer solvent phase to obtain furfural; washing solid residues to be neutral, and performing vacuum freeze drying to obtain coarse cellulose; according to the method, efficient grading separation, conversion and extraction of lignocellulose components are achieved in one pot, and the treatment process is effectively simplified. According to the better technical scheme, the concentration of furfural in the recovered upper-layer solvent phase is 10-20 g / L, and the lower-layer water phase hardly contains furfural. The content of cellulose in the coarse cellulose is 50-80%, the content of lignin is 10-31.5%, and the content of hemicellulose is 0-5.5%.

Description

Technical Field

[0001] The present invention belongs to the technical field of lignocellulosic biomass chemical engineering, and relates to a method for efficiently separating lignocellulose and simultaneously preparing furfural mediated by a temperature-controlled phase change system, specifically to a method for efficiently separating and co-producing furfural from lignocellulose components by using the temperature-controlled single-double phase transition characteristics of a high critical eutectic small molecule diol-salt biphasic system in one pot. Background Art

[0002] Agricultural waste biomass has become an important raw material resource for the sustainable production of energy and bio-based chemicals. However, the lignocellulose in biomass raw materials has a dense structure and complex composition. Direct utilization will result in high energy consumption and low selectivity of target products. Therefore, it is necessary to break its natural anti-degradation barrier through pretreatment in order to enrich cellulose for the preparation of fuels such as biodiesel and hydrogen, and at the same time, high-quality lignin phenolic substances can also be separated. For example, lignin with a relatively low degree of condensation (or uncondensed) can be directly used as a wood adhesive. Existing research shows that acid-catalyzed pretreatment of lignocellulose has a significant effect, especially Lewis acid, which not only has the advantages of being cheap and easily available, weak corrosion, environmental friendliness, and controllable catalytic activity, but also helps in the separation and synchronous upgrading transformation of lignocellulose components.

[0003] Hydrophilic two-phase substances show incompatibility under specific environmental temperatures and other conditions, and the system changes from a single phase to a two-phase, such as polymer-salt, low molecular weight alcohol-salt, etc., mainly manifested in the phase transition behavior of high critical eutectic temperature and low critical eutectic temperature. So far, most domestic and foreign research has focused on the construction and application of low critical eutectic temperature biphasic systems. For example, Roman-Leshkov et al. first proposed using a biphasic system to produce and separate furan compounds, and 5-hydroxymethylfurfural generated from fructose was successfully extracted into the organic solvent phase. Wang et al. developed a biphasic system of oxalic acid / choline chloride base and methyl isobutyl ketone to produce furfural from eucalyptus, and the furfural yield could reach 70%. Similarly, Beijing Forestry University used a biphasic system of alcohol-based deep eutectic solvents / methyl isobutyl methyl ketone to remove a large amount of lignin and hemicellulose from Eucalyptus urophylla × Eucalyptus grandis. However, the low critical eutectic biphasic system is difficult to form a phase after the temperature is lowered, thus increasing the difficulty of separating the subsequent lignocellulose dissolution products. In comparison, the high critical eutectic biphasic system has obvious advantages for lignocellulose pretreatment, but there are few reports at present. Summary of the Invention

[0004] The object of the present invention is to provide a method for efficiently separating lignocellulose and simultaneously preparing furfural mediated by a temperature-controlled phase-changing system, aiming at the problems of severe treatment conditions, cumbersome processes, and poor treatment effects existing in the existing methods for the development and utilization of all components of lignocellulose. Based on the temperature-controlled single-phase to two-phase transition characteristics of a high critical eutectic two-phase system, a novel small molecule diol-salt system is established. Under high-temperature conditions, a single-phase catalysis mediates the efficient separation of lignocellulose components and co-produces furfural. When cooled to room temperature in an ice-water bath, the single phase transforms into a two-phase state, and furfural mainly exists in the upper organic phase. The hierarchical separation of lignocellulose to enrich cellulose, the catalytic conversion of hemicellulose to produce furfural, and the separation and extraction of the product furfural are synchronously achieved in one pot, effectively shortening the treatment process.

[0005] The object of the present invention is achieved through the following technical solutions:

[0006] A method for efficiently separating lignocellulose and simultaneously preparing furfural mediated by a temperature-controlled phase-changing system, comprising: washing, drying, and pulverizing agricultural waste to obtain a material; placing the pulverized material and a small molecule diol-salt two-phase system in a reaction kettle, sealing and then performing heat treatment, after the heat treatment is completed, cooling, filtering and separating the material to obtain a filtrate and a solid residue, layering the filtrate, collecting the upper solvent phase to obtain furfural; washing the solid residue with water until neutral, and freeze-drying under vacuum to obtain crude cellulose.

[0007] The agricultural waste is at least one of bagasse and rice straw.

[0008] Preferably, the agricultural waste is washed with water, dried to a water content of 0-5%, and then pulverized to obtain a material with a particle size of 20-40 mesh.

[0009] The drying is: drying in an oven at 105°C until the water content of the material is 0-5% to avoid the influence of water in the material on the two-phase system.

[0010] The material with a particle size of 20-40 mesh obtained by pulverizing the agricultural waste. Controlling the agricultural waste within 20-40 mesh can prevent excessive pulverization of the material and cause cellulose loss.

[0011] The small molecule diol is n-butanol and polyol.

[0012] Considering that n-butanol and water need high temperature to form a single-phase system, polyol can be added for promoting dissolution, but it is necessary to avoid excessive polyol in the system causing immiscibility of n-butanol and water at low temperature. The small molecule diol-salt two-phase system is a mixture of water, n-butanol, and polyol with a volume ratio of 20:70:???10-75:20:5, preferably a mixture of 30:60:10-75:20:5.

[0013] It should be noted that there seems to be an error in the original text where "20:70:10~75:20:5" has "???" in the middle of the ratio range for the volume ratio of the small molecule diol-salt two-phase system. I have translated it as accurately as possible based on the available information.Further, considering the yield of furfural, the cellulose content in crude cellulose, and the dosage of n-butanol comprehensively, the small molecule diol-salt biphasic system is a mixture of water, n-butanol, and polyol with a volume ratio of 70:25:5 to 75:20:5 or 70:25:5 to 70:20:10.

[0014] The polyol is one of ethylene glycol or diethylene glycol.

[0015] Figure 1 It is the ternary phase diagram of the water:n-butanol:diethylene glycol system at different temperatures, which illustrates the temperature-controlled phase change process of the high critical eutectic system. It is found that: as the reaction temperature increases, the area of the interval where the water:n-butanol:diethylene glycol system stratifies into two phases gradually shrinks. For example, at 120 °C, the water:n-butanol:diethylene glycol system is almost entirely single-phase, confirming that the water:n-butanol:diethylene glycol system is a high critical eutectic biphasic system, that is, a temperature-controlled phase change system.

[0016] The salt is one of chromium chloride, iron chloride, and aluminum chloride.

[0017] The concentration of the salt in the reaction solvent is 0.01 - 0.10 mol / L, preferably 0.03 - 0.07 mol / L, and most preferably 0.05 - 0.07 mol / L.

[0018] The dosage ratio of the agricultural waste to the salt is 1:0.0002 - 1:0.002 g / moL, preferably 1:0.0006 - 1:0.0014 g / moL, and more preferably 1:0.001 - 1:0.0014 g / moL.

[0019] The reaction kettle is a high-temperature and high-pressure stainless steel reaction kettle.

[0020] The heat treatment is: heating from room temperature to 130 - 170 °C, maintaining the temperature at 130 - 170 °C, and holding the reaction for 0 - 30 min.

[0021] Preferably, the heat treatment is: heating from room temperature to 140 - 170 °C, maintaining the temperature at 140 - 170 °C, and holding the reaction for 0 - 20 min.

[0022] More preferably, the heat treatment is: heating from room temperature to 140 - 150 °C, maintaining the temperature at 140 - 150 °C, and holding the reaction for 10 - 20 min.

[0023] Most preferably, the heat treatment is: heating from room temperature to 150 °C, maintaining the temperature at 150 °C, and holding the reaction for 10 - 20 min.

[0024] During the heating and heat preservation reactions, stirring is carried out. The rotation speed of the stirring is 600 - 1000 rpm. Specifically, magnetic stirring can be adopted.

[0025] The heating method is electric heating.

[0026] The cooling method is as follows: an ice - water bath is used and the temperature is reduced to room temperature within 3 - 5 minutes.

[0027] Preferably, the cooling method is: reducing the temperature to room temperature with an ice - water bath.

[0028] The room temperature is 20 - 35 °C.

[0029] The filtrate is layered using a separating funnel.

[0030] As a preferred technical solution of the method for efficiently separating lignocellulose and simultaneously preparing furfural mediated by a temperature - controlled phase - change system of the present invention, it includes: the solvent phase is recovered by rotary evaporation to obtain n - butanol, and the n - butanol is recycled to obtain furfural.

[0031] As a preferred technical solution of the method for efficiently separating lignocellulose and simultaneously preparing furfural mediated by a temperature - controlled phase - change system of the present invention, it includes: recovering the salt in the aqueous phase by ultrafiltration.

[0032] Specifically, a method for efficiently separating lignocellulose and simultaneously preparing furfural mediated by a temperature - controlled phase - change system includes the following steps:

[0033] Step (1): Agricultural waste is washed, dried, and pulverized to obtain a material with a particle size of 20 - 40 mesh.

[0034] Step (2): The material obtained in step (1) is mixed evenly with a small - molecule diol - salt biphasic system, placed in a reaction kettle, sealed, and subjected to heat treatment: heated from room temperature to 130 - 170 °C, and kept stirring for 0 - 30 minutes, then cooled to room temperature with an ice - water bath; the material is filtered by suction to obtain a filtrate and a solid residue; the collected filtrate is layered, the upper layer is the solvent phase containing furfural, and the lower layer is the aqueous phase containing almost no furfural; the solid residue is washed with water until neutral and then vacuum freeze - dried to obtain crude cellulose.

[0035] The concentration of furfural in the solvent phase is 1 - 20 g / L, preferably 10 - 20 g / L, and the concentration of furfural in the aqueous phase is 0 - 2 g / L.

[0036] The content of cellulose in the crude cellulose is 50 - 80%, the content of hemicellulose is 0 - 5.5%, and the content of lignin is 10 - 31.5%.

[0037] The beneficial effects of the present invention are:

[0038] 1. The agricultural waste raw materials of the present invention are cheap, easily obtainable, and have a wide source, which are resources that the country focuses on developing.

[0039] 2. The high critical eutectic biphasic system (small molecule diol-salt system) of the present invention is a temperature-controlled phase change system. Under high temperature conditions, the reaction solvent is homogeneous, and the heat conduction effect is significantly improved, which can catalyze the efficient directional separation and conversion of lignocellulose components: during the heating stage, a single-phase catalysis mediates the efficient selective separation of lignocellulose components, and simultaneously catalyzes the conversion of hemicellulose into furfural; under low temperature conditions, the reaction solvent turns into a biphasic phase, and furfural enters the upper organic phase, avoiding the extraction of downstream products. The cellulose component mainly exists in the solid residue, and rapid separation and extraction of the product are obtained.

[0040] 3. The present invention realizes the efficient fractional separation, conversion, and extraction of lignocellulose components in one pot, effectively simplifying the treatment process. Under the preferred technical scheme of the present invention, the concentration of furfural in the recovered upper organic solvent phase is 10-20 g / L, and the lower aqueous phase contains almost no furfural. The cellulose content in the crude cellulose is 50-80%, the lignin content is 10-31.5%, and the hemicellulose content is 0-5.5%.

[0041] 4. The method of the present invention has mild, safe, and environmentally friendly treatment conditions. The small molecule diol of the reaction solvent and the conversion product furfural can be recovered by reduced pressure, and the salt can be recovered through a filter membrane and recycled for the pretreatment of agricultural waste. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is a phase change schematic diagram of the n-butanol-water-diethylene glycol ternary biphasic system at different reaction temperatures. [[ID=_{17]]DETAILED DESCRIPTION OF THE INVENTION

[0043] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below in conjunction with specific embodiments. Those skilled in the art can appropriately modify the process parameters under the teaching of the present invention to achieve. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art, and they are all considered to be included in the present invention.

[0044] Example 1

[0045] The sugarcane bagasse (containing 33% cellulose, 23% hemicellulose, and 39% lignin) was washed to remove sand, dried at 105 °C in a forced-air oven for 8 h until constant weight (water content was 0%), crushed by a mechanical crusher, and sieved to obtain dry materials with a particle size of 20-40 mesh.

[0046] Place 3 g of crushed bagasse, 60 mL of reaction solvent (water: n-butanol: diethylene glycol = 70:25:5 v / v / v), and chromium(III) chloride hexahydrate in a 100 mL quartz inner liner. The concentration of chromium(III) chloride hexahydrate in the reaction solvent is 0.05 mol / L. Then, place the quartz inner liner into a stainless steel magnetic stirring reactor (100 mL; NSG100-P5-T3-SS1-SV-R, Anhui Kemi Instrument Co., Ltd.), seal the reactor body, and perform heat treatment: Use electric heating to raise the temperature from room temperature to 150 °C within 30 min, keep the temperature at 150 °C for 20 min, and stir magnetically throughout the process (600 rpm); Take out the reactor body, cool it to room temperature in an ice-water bath for 3 min, open the reactor lid, take out the quartz inner liner, and use a sintered glass funnel (G1-100 mL) for vacuum filtration to collect the filtrate and solid residue respectively.

[0047] Put the filtrate into a separatory funnel, let it stand at room temperature for 30 min, and separate naturally. The upper layer is the n-butanol phase, and the lower layer is the water phase. The furfural content in the n-butanol phase and water phase is shown in Table 1.

[0048] Wash the solid residue with deionized water twice (150 mL each time) until the filtrate is neutral to obtain crude cellulose. The cellulose, hemicellulose, and lignin contents in the crude cellulose are shown in Table 1.

[0049] Example 2

[0050] Place 3 g of crushed bagasse (the same as in Example 1), 60 mL of reaction solvent (water: n-butanol: diethylene glycol = 70:25:5 v / v / v), and chromium(III) chloride hexahydrate in a 100 mL quartz inner liner. The concentration of chromium(III) chloride hexahydrate in the reaction solvent is 0.05 mol / L. Then, place the quartz inner liner into a stainless steel magnetic stirring reactor (100 mL; NSG100-P5-T3-SS1-SV-R, Anhui Kemi Instrument Co., Ltd.), seal the reactor body, and perform heat treatment: Use electric heating to raise the temperature from room temperature to 170 °C within 30 min, keep the temperature at 170 °C for 20 min, and stir magnetically throughout the process (600 rpm); Take out the reactor body, cool it to room temperature in an ice-water bath for 3 min, open the reactor lid, take out the quartz inner liner, and use a sintered glass funnel (G1-100 mL) for vacuum filtration to collect the filtrate and solid residue respectively.

[0051] Put the filtrate into a separatory funnel, let it stand at room temperature for 30 min, and separate naturally. The upper layer is the n-butanol phase, and the lower layer is the water phase. The furfural content in the n-butanol phase and water phase is shown in Table 1.

[0052] Wash the solid residue with deionized water twice (150 mL each time) until the filtrate is neutral to obtain crude cellulose. The cellulose, hemicellulose, and lignin contents in the crude cellulose are shown in Table 1.

[0053] Example 3

[0054] Place 3 g of crushed bagasse (same as in Example 1), 60 mL of reaction solvent (water:n-butyl alcohol:diethylene glycol = 70:25:5 v / v / v), and chromium(III) chloride hexahydrate in a 100 mL quartz inner liner. The concentration of chromium(III) chloride hexahydrate in the reaction solvent is 0.07 mol / L. Then, place the quartz inner liner into a stainless steel magnetic stirring reaction kettle (100 mL; NSG100-P5-T3-SS1-SV-R, Anhui Kemi Instrument Co., Ltd.). Seal the kettle body and conduct heat treatment: Use electric heating to raise the temperature from room temperature to 150 °C within 30 min, hold at 150 °C for 20 min, and stir magnetically throughout the process (600 rpm). Take out the kettle body, cool it in an ice-water bath for 3 min, cool it to room temperature, open the kettle lid, take out the quartz inner liner, and use a sintered glass funnel (G1-100 mL) for vacuum filtration. Collect the filtrate and solid residue separately.

[0055] Put the filtrate into a separatory funnel, let it stand at room temperature for 30 min, and it will separate naturally. The upper layer is the n-butyl alcohol phase, and the lower layer is the water phase. The furfural content in the n-butyl alcohol phase and the water phase is shown in Table 1.

[0056] Wash the solid residue with deionized water twice (150 mL each time) until the filtrate is neutral to obtain crude cellulose. The cellulose, hemicellulose, and lignin contents in the crude cellulose are shown in Table 1.

[0057] Comparative Example 1

[0058] Place 3 g of crushed bagasse (same as in Example 1) and 60 mL of reaction solvent (water:n-butyl alcohol:diethylene glycol = 70:25:5 v / v / v) in a 100 mL quartz inner liner. Then, place the quartz inner liner into a stainless steel magnetic stirring reaction kettle (100 mL; NSG100-P5-T3-SS1-SV-R, Anhui Kemi Instrument Co., Ltd.). Seal the kettle body and conduct heat treatment: Use electric heating to raise the temperature from room temperature to 150 °C within 30 min, hold at 150 °C for 20 min, and stir magnetically throughout the process (600 rpm). Take out the kettle body, cool it in an ice-water bath for 3 min, cool it to room temperature, open the kettle lid, take out the quartz inner liner, and use a sintered glass funnel (G1-100 mL) for vacuum filtration. Collect the filtrate and solid residue separately.

[0059] Put the filtrate into a separatory funnel, let it stand at room temperature for 30 min, and it will separate naturally to obtain the upper n-butyl alcohol phase and the lower water phase. The furfural content in the n-butyl alcohol phase and the water phase is shown in Table 1.

[0060] Wash the solid residue with deionized water twice (150 mL each time) until the filtrate is neutral to obtain crude cellulose. The cellulose, hemicellulose, and lignin contents in the crude cellulose are shown in Table 1.

[0061] Example 4

[0062] Place 3 g of crushed bagasse (same as in Example 1), 60 mL of reaction solvent (water:n-butyl alcohol:diethylene glycol = 70:25:5 v / v / v), and aluminum chloride hexahydrate in a 100 mL quartz inner liner. The concentration of aluminum chloride hexahydrate in the reaction solvent is 0.05 mol / L. Then place the quartz inner liner into a stainless steel magnetic stirring reaction kettle (100 mL; NSG100-P5-T3-SS1-SV-R, Anhui Kemi Instrument Co., Ltd.). Seal the kettle body and conduct heat treatment: Use electric heating to raise the temperature from room temperature to 150 °C within 30 min, hold at 150 °C for 20 min, and stir magnetically throughout the process (600 rpm); Take out the kettle body, cool it to room temperature in an ice-water bath for 3 min, open the kettle lid, take out the quartz inner liner, and use a sintered glass funnel (G1-100 mL) for vacuum filtration to collect the filtrate and solid residue respectively.

[0063] Put the filtrate into a separatory funnel, let it stand at room temperature for 30 min, and it will separate naturally. The upper layer is the n-butyl alcohol phase, and the lower layer is the water phase. The furfural contents in the n-butyl alcohol phase and water phase are shown in Table 1.

[0064] Wash the solid residue with deionized water twice (150 mL each time) until the filtrate is neutral to obtain crude cellulose. The cellulose, hemicellulose, and lignin contents in the crude cellulose are shown in Table 1.

[0065] Example 5

[0066] Place 3 g of crushed bagasse (same as in Example 1), 60 mL of reaction solvent (water:n-butyl alcohol:diethylene glycol = 70:25:5 v / v / v), and ferric chloride hexahydrate in a 100 mL quartz inner liner. The concentration of ferric chloride hexahydrate in the reaction solvent is 0.05 mol / L. Then place the quartz inner liner into a stainless steel magnetic stirring reaction kettle (100 mL; NSG100-P5-T3-SS1-SV-R, Anhui Kemi Instrument Co., Ltd.). Seal the kettle body and conduct heat treatment: Use electric heating to raise the temperature from room temperature to 150 °C within 30 min, hold at 150 °C for 20 min, and stir magnetically throughout the process (600 rpm); Take out the kettle body, cool it to room temperature in an ice-water bath for 3 min, open the kettle lid, take out the quartz inner liner, and use a sintered glass funnel (G1-100 mL) for vacuum filtration to collect the filtrate and solid residue respectively.

[0067] Put the filtrate into a separatory funnel, let it stand at room temperature for 30 min, and it will separate naturally. The upper layer is the n-butyl alcohol phase, and the lower layer is the water phase. The furfural contents in the n-butyl alcohol phase and water phase are shown in Table 1.

[0068] Wash the solid residue with deionized water twice (150 mL each time) until the filtrate is neutral to obtain crude cellulose. The cellulose, hemicellulose, and lignin contents in the crude cellulose are shown in Table 1.

[0069] Example 6

[0070] Place 3 g of crushed bagasse (same as in Example 1), 60 mL of reaction solvent (water:n-butyl alcohol:diethylene glycol = 45:45:10 v / v / v), and chromium(III) chloride hexahydrate in a 100 mL quartz inner liner. The concentration of chromium(III) chloride hexahydrate in the reaction solvent is 0.05 mol / L. Then, place the quartz inner liner into a stainless-steel magnetic stirring reactor (100 mL; NSG100-P5-T3-SS1-SV-R, Anhui Kemi Instruments Co., Ltd.). Seal the reactor body and perform heat treatment: Use electric heating to raise the temperature from room temperature to 150 °C within 30 min, hold at 150 °C for 20 min, and stir magnetically throughout the process (600 rpm). Take out the reactor body, cool it in an ice-water bath for 3 min, cool to room temperature, open the reactor lid, take out the quartz inner liner, and use a sintered glass funnel (G1-100 mL) for vacuum filtration. Collect the filtrate and solid residue separately.

[0071] Put the filtrate into a separatory funnel and let it stand at room temperature for 30 min. It will separate naturally into layers. The upper layer is the n-butyl alcohol phase, and the lower layer is the water phase. The furfural contents in the n-butyl alcohol phase and water phase are shown in Table 1.

[0072] Wash the solid residue with deionized water twice (150 mL each time) until the filtrate is neutral to obtain crude cellulose. The cellulose, hemicellulose, and lignin contents in the crude cellulose are shown in Table 1.

[0073] Example 7

[0074] Place 3 g of crushed bagasse (same as in Example 1), 60 mL of reaction solvent (water:n-butyl alcohol:diethylene glycol = 30:60:10 v / v / v), and chromium(III) chloride hexahydrate in a 100 mL quartz inner liner. The concentration of chromium(III) chloride hexahydrate in the reaction solvent is 0.05 mol / L. Then, place the quartz inner liner into a stainless-steel magnetic stirring reactor (100 mL; NSG100-P5-T3-SS1-SV-R, Anhui Kemi Instruments Co., Ltd.). Seal the reactor body and perform heat treatment: Use electric heating to raise the temperature from room temperature to 150 °C within 30 min, hold at 150 °C for 20 min, and stir magnetically throughout the process (600 rpm). Take out the reactor body, cool it in an ice-water bath for 3 min, cool to room temperature, open the reactor lid, take out the quartz inner liner, and use a sintered glass funnel (G1-100 mL) for vacuum filtration. Collect the filtrate and solid residue separately.

[0075] Put the filtrate into a separatory funnel and let it stand at room temperature for 30 min. It will separate naturally into layers. The upper layer is the n-butyl alcohol phase, and the lower layer is the water phase. The furfural contents in the n-butyl alcohol phase and water phase are shown in Table 1.

[0076] Wash the solid residue with deionized water twice (150 mL each time) until the filtrate is neutral to obtain crude cellulose. The cellulose, hemicellulose, and lignin contents in the crude cellulose are shown in Table 1.

[0077] Example 8

[0078] Load 3 g of crushed bagasse (same as in Example 1), 60 mL of reaction solvent (water:n-butyl alcohol:diethylene glycol = 35:55:10 v / v / v), and chromium(III) chloride hexahydrate into a 100 mL quartz inner liner. The concentration of chromium(III) chloride hexahydrate in the reaction solvent is 0.05 mol / L. Then place the quartz inner liner into a stainless steel magnetic stirring reaction kettle (100 mL; NSG100-P5-T3-SS1-SV-R, Anhui Kemi Instruments Co., Ltd.). Seal the kettle body and conduct heat treatment: Use electric heating to raise the temperature from room temperature to 150 °C within 30 min, keep it at 150 °C for 20 min, and stir magnetically throughout the process (600 rpm). Take out the kettle body, cool it to room temperature in an ice-water bath for 3 min, open the kettle lid, take out the quartz inner liner, and use a sintered glass funnel (G1-100 mL) for vacuum filtration. Collect the filtrate and solid residue separately.

[0079] Put the filtrate into a separating funnel and let it stand at room temperature for 30 min. It will separate naturally into layers. The upper layer is the n-butyl alcohol phase, and the lower layer is the water phase. The furfural content in the n-butyl alcohol phase and water phase is shown in Table 1.

[0080] Wash the solid residue with deionized water twice (150 mL each time) until the filtrate is neutral to obtain crude cellulose. The cellulose, hemicellulose, and lignin contents in the crude cellulose are shown in Table 1.

[0081] Example 9

[0082] Load 3 g of crushed bagasse (same as in Example 1), 60 mL of reaction solvent (water:n-butyl alcohol:diethylene glycol = 70:25:5 v / v / v), and chromium(III) chloride hexahydrate into a 100 mL quartz inner liner. The concentration of chromium(III) chloride hexahydrate in the reaction solvent is 0.05 mol / L. Then place the quartz inner liner into a stainless steel magnetic stirring reaction kettle (100 mL; NSG100-P5-T3-SS1-SV-R, Anhui Kemi Instruments Co., Ltd.). Seal the kettle body and conduct heat treatment: Use electric heating and ensure uniform mixing by magnetic stirring (600 rpm) throughout the process. Raise the temperature from room temperature to 150 °C within 30 min, then immediately take out the kettle body, cool it to room temperature in an ice-water bath for 3 min, open the kettle lid, take out the quartz inner liner, and use a sintered glass funnel (G1-100 mL) for vacuum filtration. Collect the filtrate and solid residue separately.

[0083] Put the filtrate into a separating funnel and let it stand at room temperature for 30 min. It will separate naturally into layers. The upper layer is the n-butyl alcohol phase, and the lower layer is the water phase. The furfural content in the n-butyl alcohol phase and water phase is shown in Table 1.

[0084] Wash the solid residue with deionized water twice (150 mL each time) until the filtrate is neutral to obtain crude cellulose. The cellulose, hemicellulose, and lignin contents in the crude cellulose are shown in Table 1.

[0085] Example 10

[0086] Place 3 g of crushed bagasse (same as in Example 1), 60 mL of reaction solvent (water:n-butyl alcohol:diethylene glycol = 70:20:10 v / v / v), and chromium(III) chloride hexahydrate in a 100 mL quartz inner liner. The concentration of chromium(III) chloride hexahydrate in the reaction solvent is 0.05 mol / L. Then, place the quartz inner liner into a stainless-steel magnetic stirring reaction kettle (100 mL; NSG100-P5-T3-SS1-SV-R, Anhui Kemi Instruments Co., Ltd.). Seal the kettle body and conduct heat treatment: Use electric heating to raise the temperature from room temperature to 150 °C within 30 min, hold at 150 °C for 20 min, and stir magnetically throughout the process (600 rpm). Take out the kettle body, cool it to room temperature in an ice-water bath for 3 min, open the kettle lid, take out the quartz inner liner, and use a sintered glass funnel (G1-100 mL) for vacuum filtration. Collect the filtrate and solid residue separately.

[0087] Put the filtrate into a separatory funnel, let it stand at room temperature for 30 min, and allow it to separate naturally. The upper layer is the n-butyl alcohol phase, and the lower layer is the water phase. The furfural content in the n-butyl alcohol phase and water phase is shown in Table 1.

[0088] Wash the solid residue with deionized water twice (150 mL each time) until the filtrate is neutral to obtain crude cellulose. The cellulose, hemicellulose, and lignin contents in the crude cellulose are shown in Table 1.

[0089] Example 11

[0090] Place 3 g of crushed bagasse (same as in Example 1), 60 mL of reaction solvent (water:n-butyl alcohol:ethylene glycol = 70:25:5 v / v / v), and chromium(III) chloride hexahydrate in a 100 mL quartz inner liner. The concentration of chromium(III) chloride hexahydrate in the reaction solvent is 0.05 mol / L. Then, place the quartz inner liner into a stainless-steel magnetic stirring reaction kettle (100 mL; NSG100-P5-T3-SS1-SV-R, Anhui Kemi Instruments Co., Ltd.). Seal the kettle body and conduct heat treatment: Use electric heating to raise the temperature from room temperature to 150 °C within 30 min, hold at 150 °C for 20 min, and stir magnetically throughout the process (600 rpm). Take out the kettle body, cool it to room temperature in an ice-water bath for 3 min, open the kettle lid, take out the quartz inner liner, and use a sintered glass funnel (G1-100 mL) for vacuum filtration. Collect the filtrate and solid residue separately.

[0091] Put the filtrate into a separatory funnel, let it stand at room temperature for 30 min, and allow it to separate naturally. The upper layer is the n-butyl alcohol phase, and the lower layer is the water phase. The furfural content in the n-butyl alcohol phase and water phase is shown in Table 1.

[0092] Wash the solid residue with deionized water twice (150 mL each time) until the filtrate is neutral to obtain crude cellulose. The cellulose, hemicellulose, and lignin contents in the crude cellulose are shown in Table 1.

[0093] Example 12

[0094] Rice straw (containing 29% cellulose, 18% hemicellulose and 18% lignin) is washed with water to remove sand, dried in a blast dryer at 105 °C for 8 h to constant weight (water content is 0%), crushed by a mechanical crusher, and sieved to obtain a dry material with a particle size of 20 - 40 mesh.

[0095] 3 g of crushed rice straw, 60 mL of reaction solvent (water: n-butanol: diethylene glycol = 70:25:5 v / v / v), and chromium(III) chloride hexahydrate are placed in a 100 mL quartz inner liner. The concentration of chromium(III) chloride hexahydrate in the reaction solvent is 0.05 mol / L. Then, the quartz inner liner is placed in a stainless steel magnetic stirring reactor (100 mL; NSG100 - P5 - T3 - SS1 - SV - R, Anhui Kemi Instrument Co., Ltd.). The reactor body is sealed and heated as follows: Electric heating is used to raise the temperature from room temperature to 150 °C within 30 min, and then keep it at 150 °C for 20 min with magnetic stirring throughout the process (600 rpm). The reactor body is taken out, cooled to room temperature in an ice - water bath for 3 min, the reactor lid is opened, the quartz inner liner is taken out, and vacuum filtration is carried out using a sintered glass funnel (G1 - 100 mL) to collect the filtrate and solid residue respectively.

[0096] The filtrate is placed in a separating funnel and left to stand at room temperature for 30 min for natural stratification. The upper layer is the n - butanol phase and the lower layer is the water phase. The furfural contents in the n - butanol phase and water phase are shown in Table 1.

[0097] The solid residue is washed twice with deionized water (150 mL each time) until the filtrate is neutral to obtain crude cellulose. The cellulose, hemicellulose, and lignin contents in the crude cellulose are shown in Table 1.

[0098] Table 1. Separation and conversion effects of lignocellulose components under different reaction conditions in the small - molecule diol - salt system

[0099]

Claims

1. A method for efficiently separating lignocellulose and simultaneously preparing furfural mediated by a temperature-controlled phase change system, characterized in that: Comprising: Agricultural waste is washed, dried, and pulverized to obtain a material; the pulverized material and a small molecule diol-salt biphasic system are placed in a reaction kettle, sealed, and then subjected to heat treatment. After the heat treatment is completed, it is cooled, and the material is separated by suction filtration to obtain a filtrate and a solid residue. The filtrate is phase-separated, and the upper solvent phase is collected to obtain furfural; the solid residue is washed with water until neutral and then freeze-dried under vacuum to obtain crude cellulose.

2. The method for efficiently separating lignocellulose and simultaneously preparing furfural mediated by a temperature-controlled phase change system according to claim 1, characterized in that: The agricultural waste is at least one of bagasse and rice straw.

3. The method for efficiently separating lignocellulose and simultaneously preparing furfural mediated by a temperature-controlled phase change system according to claim 1, characterized in that: The agricultural waste is washed with water, dried to a water content of 0-5%, and then pulverized to obtain a material with a mesh size of 20-40.

4. The method for efficiently separating lignocellulose and simultaneously preparing furfural mediated by a temperature-controlled phase-change system according to claim 1, wherein: The small molecule diol-salt biphasic system is a mixture of water, n-butanol, and polyol with a volume ratio of 20:70:10 to 75:20:5, preferably a mixture of 30:60:10 to 75:20:5, and more preferably a mixture of 70:25:5 to 75:20:5 or 70:25:5 to 70:20:

10.

5. The method for efficiently separating lignocellulose and simultaneously preparing furfural mediated by a temperature-controlled phase change system according to claim 4, wherein: The polyol is one of ethylene glycol or diethylene glycol.

6. The method for efficiently separating lignocellulose and simultaneously preparing furfural mediated by a temperature-controlled phase change system according to claim 1, characterized in that: The salt is one of chromium chloride, iron chloride, and aluminum chloride; the dosage ratio of the agricultural waste to the salt is 1:0.0002 to 1:0.002 g / moL; the concentration of the salt in the reaction solvent is 0.01 to 0.10 mol / L.

7. The method for efficiently separating lignocellulose and simultaneously preparing furfural mediated by a temperature-controlled phase change system according to claim 6, wherein: The concentration of the salt in the reaction solvent is 0.03 to 0.07 mol / L, preferably 0.05 to 0.07 mol / L.

8. The method for efficiently separating lignocellulose and simultaneously preparing furfural mediated by a temperature-controlled phase change system according to claim 1, characterized in that: The dosage ratio of the agricultural waste to the salt is 1:0.0006 to 1:0.0014 g / moL, preferably 1:0.001 to 1:0.0014 g / moL.

9. The method for efficiently separating lignocellulose and simultaneously preparing furfural mediated by a temperature-controlled phase change system according to claim 1, wherein: The heat treatment is as follows: heating from room temperature to 130-170 °C, maintaining the temperature at 130-170 °C, and holding the reaction for 0-30 min; preferably, the heat treatment is: heating from room temperature to 140-170 °C, maintaining the temperature at 140-170 °C, and holding the reaction for 0-20 min; more preferably, the heat treatment is: heating from room temperature to 140-150 °C, maintaining the temperature at 140-150 °C, and holding the reaction for 10-20 min.

10. The method for efficiently separating lignocellulose and simultaneously preparing furfural mediated by a temperature-controlled phase change system according to claim 1, characterized in that: The cooling is as follows: using an ice-water bath and cooling to room temperature within 3-5 min.

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