A cellulosic fiber, a method for preparing the same and a method for preparing furanic chemicals

Abstract

The present application belongs to the technical field of biomass utilization, and provides holocellulose, a preparation method thereof and a method for preparing furan chemicals. The method comprises the following steps: reacting lignocellulose raw materials and a deep eutectic solvent (DES) in a mass ratio of 2-6:60 to obtain holocellulose. The alkaline DES composed of Lys and MEA achieves the best treatment effect on the larch raw materials, and high-purity larch holocellulose and a lignin removal rate are obtained; a double-acid catalytic system composed of heteropoly acid and AlCl3 catalyzes the conversion of larch holocellulose into furan chemicals in a two-phase solvent composed of water and methyl isobutyl ketone (MIBK), and the holocellulose achieves efficient conversion, and the yield of 5-hydroxymethylfurfural (HMF) and furfural (FF) is high; the aqueous solution of the polyacid catalyst and AlCl3 can be recycled, and still maintains high catalytic performance after five cycles.

Description

Technical Field

[0001] This invention relates to the field of biomass utilization technology, and in particular to a holocellulose, a method for preparing the same, and a method for preparing furan chemicals. Background Technology

[0002] Agricultural and forestry processing industries generate large amounts of agricultural and forestry waste. Currently, the utilization efficiency of these lignocellulose-rich wastes is low, mainly relying on methods such as incineration for heat generation and composting, which have low utilization value and cause environmental pollution. Collecting wood resource residues and further converting them for the production of high-value-added products such as liquid fuels, pharmaceuticals, and platform chemicals will greatly improve the utilization efficiency of wood resources, effectively avoiding resource waste and aligning with the research trend of coordinated planning for biomass production and utilization efficiency. To improve the utilization efficiency of lignocellulose, it is necessary to address the challenges of its strong resistance to biodegradation and the difficulty of separation, in order to meet the needs of the high-value utilization of lignocellulose biomass.

[0003] Among traditional treatment methods, physical methods are simple to operate, fast, and produce little pollution, especially microwave methods which significantly shorten processing time. However, physical methods suffer from high equipment costs and energy consumption, as well as safety hazards. Biological methods for degrading and separating lignocellulose components have advantages such as low cost and energy consumption, high specificity, and mild conditions, but they also have disadvantages such as long processing cycles and low bio-enzyme yield and processing efficiency. Chemical pretreatment has good treatment effects, but it requires highly corrosive equipment, and solvent recovery is difficult and can easily cause environmental pollution. Eutectic solvents (DES) can overcome the shortcomings of chemical and biological methods to some extent and can be used to treat lignocellulose biomass.

[0004] 5-Hydroxymethylfurfural (HMF) is widely considered a key element in narrowing the gap between fossil fuel economies and sustainable economies; furfural (FF) has been selected as one of the top 30 biomass-derived platform compounds based on factors such as raw materials, processing costs, technological complexity, and market potential. Traditional methods for catalytically preparing HMF and FF from biomass primarily rely on dilute acid catalysis. Dilute acid solutions (such as low-concentration HCl or H2SO4 solutions) are suitable for depolymerizing cellulose and hemicellulose, but they generate large amounts of acidic pollutants and cause equipment corrosion. Due to the strong acidity of heteropoly acids (HPA), H3PW... 12 O 40 HPA, as exemplified by [example catalyst], is used to prepare furfural compounds. Furthermore, homogeneous catalysts suffer from the drawback of being difficult to recover, which is detrimental to controlling production costs; heterogeneous catalysts also suffer from the drawback of low mass transfer efficiency.

[0005] Therefore, combining HPA with a temperature-controlled catalyst to achieve homogeneous reaction by dissolving at high temperature and recovering by precipitation at low temperature is of great significance. This achieves both high-efficiency catalytic reaction and catalyst recovery. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art by providing holocellulose, a method for preparing the same, and a method for preparing furan chemicals.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0008] This invention provides a method for preparing holocellulose, comprising the following steps:

[0009] Lignocellulose raw materials are reacted with a eutectic solvent to obtain holocellulose;

[0010] The mass ratio of the lignocellulose raw material to the eutectic solvent is 2-6:60; the eutectic solvent is composed of lysine and ethanolamine.

[0011] Preferably, the reaction temperature is 80–120°C and the reaction time is 6–9 hours.

[0012] Preferably, the reaction mixture obtained from the reaction is subjected to solid-liquid separation, and the separated filter residue is washed and dried in sequence to obtain holocellulose.

[0013] Preferably, the washing reagents are, in order, an aqueous solution of acetone and water, wherein the volume ratio of acetone to water in the aqueous solution of acetone is 6-8:2-4; and the drying temperature is 70-90°C.

[0014] The present invention also provides holocellulose prepared by the aforementioned preparation method.

[0015] The present invention also provides a method for preparing furan chemicals from holocellulose, comprising the following steps: reacting holocellulose, aluminum chloride, polyacid catalyst, water and methyl isobutyl ketone to obtain furan chemicals.

[0016] Preferably, the mass ratio of holocellulose, aluminum chloride and polyacid catalyst is 1:0.15-0.25:0-3; and the volume ratio of water and methyl isobutyl ketone is 1-4:6-19.

[0017] Preferably, the reaction temperature is 120–170°C, the reaction time is 7–12 h, and the reaction is carried out under stirring conditions at a stirring rate of 400–600 rpm.

[0018] Preferably, the polyacid catalyst is a temperature-controlled polyacid catalyst, and the chemical formula of the temperature-controlled polyacid catalyst is Ch. n H3-n PW 12 O 40 , where n is 1, 2 or 3.

[0019] Preferably, the preparation method of the temperature-controlled polyacid catalyst is as follows: adding an aqueous solution of choline chloride dropwise to an aqueous solution of phosphotungstic acid to carry out the reaction, obtaining a solid precipitate, washing the solid precipitate and drying it to obtain the temperature-controlled polyacid catalyst;

[0020] The molar ratio of choline chloride to phosphotungstic acid is 1–3:1; the concentration of the aqueous solution of choline chloride is 0.15–0.25 mol / L, and the concentration of the aqueous solution of phosphotungstic acid is 0.04–0.06 mol / L.

[0021] The beneficial effects of this invention include the following:

[0022] The method of this invention uses an alkaline DES composed of Lys and MEA to achieve optimal treatment of larch raw materials, obtaining high purity larch holocellulose and lignin removal rates; a dual-acid catalytic system composed of heteropolyacids and AlCl3 catalyzes the conversion of larch holocellulose into furan chemicals in a two-phase solvent composed of water and MIBK, achieving efficient conversion of holocellulose and high yields of HMF and FF; the polyacid catalyst and the aqueous solution of AlCl3 are recycled and reused, maintaining high catalytic performance even after five cycles. Attached Figure Description

[0023] Figure 1 SEM images of larch raw material and holocellulose from Example 1 are shown, where a and c are larch raw material at different magnifications, and b and d are larch holocellulose at different magnifications.

[0024] Figure 2 The graph shows the yield, conversion, and cycle performance of the temperature-controlled polyacid catalyst used in Example 1 for the preparation of furan chemicals from holocellulose. Detailed Implementation

[0025] This invention provides a method for preparing holocellulose, comprising the following steps:

[0026] Lignocellulose raw materials are reacted with a eutectic solvent (DES) to obtain holocellulose;

[0027] The mass ratio of the lignocellulose raw material to DES is 2-6:60; the DES is composed of lysine and ethanolamine.

[0028] In this invention, the mass ratio of the lignocellulose raw material to DES is preferably 3 to 5:60, and more preferably 4:60.

[0029] In the DES of the present invention, the molar ratio of lysine (Lys) to ethanolamine (MEA) is preferably 1:5 to 7.

[0030] In this invention, the reaction temperature is preferably 80-120°C, more preferably 90-110°C, and even more preferably 100°C; the reaction time is preferably 6-9 hours, more preferably 7-8 hours; and the reaction is carried out under stirring conditions.

[0031] In this invention, the reaction mixture obtained from the reaction is preferably subjected to solid-liquid separation, and the separated filter residue is preferably washed and dried sequentially to obtain holocellulose.

[0032] In this invention, the washing reagents are preferably acetone aqueous solution and water in sequence. In the acetone aqueous solution, the volume ratio of acetone to water is preferably 6-8:2-4, and more preferably 7:3. The purpose of washing with acetone aqueous solution is to remove residual DES, and washing with water makes the filter residue neutral.

[0033] In this invention, the drying temperature is preferably 70-90°C, more preferably 75-85°C, and even more preferably 80°C; the drying is preferably vacuum drying.

[0034] The present invention also provides holocellulose prepared by the aforementioned preparation method.

[0035] The present invention also provides a method for preparing furan chemicals from holocellulose, comprising the following steps: reacting holocellulose, aluminum chloride, polyacid catalyst, water and methyl isobutyl ketone (MIBK) to obtain furan chemicals.

[0036] In this invention, the mass ratio of holocellulose, aluminum chloride and polyacid catalyst is preferably 1:0.15-0.25:0-3, more preferably 1:0.18-0.22:1-2, and even more preferably 1:0.2:1.5; the volume ratio of water and MIBK is preferably 1-4:6-19, more preferably 2-3:8-15, and even more preferably 2.5:10-13.

[0037] In this invention, the reaction temperature is preferably 120–170°C, more preferably 130–160°C, and even more preferably 140–150°C; the reaction time is preferably 7–12 h, more preferably 8–11 h, and even more preferably 9–10 h; the reaction is preferably carried out under stirring conditions, and the stirring rate is preferably 400–600 rpm, more preferably 450–550 rpm, and even more preferably 500 rpm.

[0038] In this invention, the polyacid catalyst is preferably a temperature-controlled polyacid catalyst, and the chemical formula of the temperature-controlled polyacid catalyst is preferably Ch. n H 3-n PW12 O 40 , where n is 1, 2 or 3.

[0039] In this invention, the preparation method of the temperature-controlled polyacid catalyst is as follows: adding an aqueous solution of choline chloride dropwise to an aqueous solution of phosphotungstic acid to carry out the reaction, obtaining a solid precipitate, washing the solid precipitate and drying it to obtain the temperature-controlled polyacid catalyst;

[0040] The molar ratio of choline chloride to phosphotungstic acid is preferably 1 to 3:1, more preferably 1:1, 2:1 or 3:1; the concentration of the choline chloride aqueous solution is preferably 0.15 to 0.25 mol / L, more preferably 0.18 to 0.22 mol / L, and even more preferably 0.2 mol / L; the concentration of the phosphotungstic acid aqueous solution is preferably 0.04 to 0.06 mol / L, more preferably 0.045 to 0.055 mol / L, and even more preferably 0.05 mol / L.

[0041] In this invention, the reaction temperature is preferably room temperature, the reaction time is preferably 10-14 h, more preferably 11-13 h, and even more preferably 12 h; the drying time is preferably 10-14 h, more preferably 11-13 h, and even more preferably 12 h.

[0042] In this invention, the mixture obtained from the reaction is preferably centrifuged to obtain three layers: the upper layer is an organic phase containing furan, the middle layer is an aqueous phase, and the lower layer is solid residue and catalyst.

[0043] In this invention, the solid residue and catalyst are preferably stirred and then filtered while hot, and the filtered residue is washed and dried. The stirring temperature is preferably 70-90°C, more preferably 75-85°C, and even more preferably 80°C.

[0044] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0045] Example 1

[0046] Preparation of alkaline DES: Lys and MEA in a molar ratio of 1:6 were mixed in a round-bottom flask and then stirred at 500 rpm in a constant-temperature magnetic stirring bath at 80°C until a homogeneous and transparent liquid was formed. After the alkaline DES solvent was cooled to room temperature, it was stored in a desiccator for later use.

[0047] Preparation of larch holocellulose: 4g of larch raw material and 60g of alkaline DES solvent were mixed evenly in a round-bottom flask and stirred continuously at 500rpm for 8h at 100℃. After the reaction was completed, the mixture was rapidly cooled to room temperature. The reaction mixture was separated into solid and liquid phases by vacuum filtration (pressure 0.5MPa). The filter residue was thoroughly washed with an acetone-water solution (acetone to water volume ratio 7:3) to remove residual DES solvent, and then washed with deionized water until neutral. The washed filter residue was collected and transferred to a vacuum drying oven (vacuum degree 0.05MPa) and dried at 80℃ to obtain larch holocellulose.

[0048] Temperature-controlled polyacid catalyst ChH2PW 12 O 40 Synthesis: Dissolve 1 mmol of choline chloride in 5 mL of deionized water and stir until the choline chloride is completely dissolved. Simultaneously, take 1 mmol of H3PW... 12 O 40 Dissolve in 20 mL of deionized water and stir until H3PW 12 O 40 Completely dissolve. Then, add choline chloride aqueous solution dropwise to H3PW at a rate of 10 mL / min. 12 O 40 In the aqueous solution, the mixture was stirred at room temperature for 12 hours, and then filtered to separate a white solid precipitate, which was washed three times with deionized water. The white solid precipitate was then dried in a vacuum drying oven (vacuum degree of 0.05 MPa) for 12 hours to obtain ChH2PW. 12 O 40 catalyst.

[0049] Preparation of furan chemicals: 0.1 g holocellulose, 0.02 g AlCl3, 0.15 g catalyst, 10 mL deionized water, and a mixture of MIBK were added to a reactor (the volume ratio of deionized water to MIBK was 2.5:13). The mixture was stirred at 150 °C and 500 rpm for 9 h. After the reaction, the mixture was rapidly cooled to room temperature and centrifuged. After centrifugation, the reaction mixture separated into three layers: the upper layer was the organic phase containing the product, the middle layer was the aqueous phase, and the lower layer was the solid residue and catalyst. The solid residue and catalyst were placed in hot water at 85 °C, stirred, and filtered while hot. The filter residue was washed, dried, and weighed to calculate the conversion rate of holocellulose. The catalyst precipitated after the hot aqueous solution cooled to room temperature; the catalyst was washed, dried, and recycled.

[0050] Example 2

[0051] Preparation of alkaline DES: Lys and MEA in a molar ratio of 1:6 were mixed in a round-bottom flask and then stirred at 450 rpm in a constant-temperature magnetic stirring bath at 80°C until a homogeneous and transparent liquid was formed. The alkaline DES solvent was cooled to room temperature and stored in a desiccator for later use.

[0052] Preparation of larch holocellulose: 3g of larch raw material and 60g of alkaline DES solvent were mixed evenly in a round-bottom flask and stirred continuously at 450rpm for 9h at 90℃. After the reaction was completed, the mixture was rapidly cooled to room temperature. The reaction mixture was separated into solid and liquid phases by vacuum filtration (pressure 0.5MPa). The filter residue was thoroughly washed with an acetone-water solution (acetone to water volume ratio 6:2) to remove residual DES solvent, and then washed with deionized water until neutral. The washed filter residue was collected and transferred to a vacuum drying oven (vacuum degree 0.05MPa) and dried at 75℃ to obtain larch holocellulose.

[0053] Temperature-controlled polyacid catalyst Ch2HPW 12 O 40 Synthesis: Dissolve 2 mmol of choline chloride in 10 mL of deionized water and stir until the choline chloride is completely dissolved. Simultaneously, take 1 mmol of H3PW... 12 O 40 Dissolve in 20 mL of deionized water and stir until H3PW 12 O 40 Completely dissolve. Then, add choline chloride aqueous solution dropwise to H3PW at a rate of 10 mL / min. 12 O 40 In the aqueous solution, the mixture was stirred at room temperature for 11 hours, then filtered to separate a white solid precipitate, which was washed four times with deionized water. The white solid precipitate was then dried in a vacuum drying oven (vacuum degree of 0.05 MPa) for 12 hours to obtain Ch2HPW. 12 O 40 catalyst.

[0054] Preparation of furan chemicals: 0.1 g holocellulose, 0.018 g AlCl3, 0.1 g catalyst, 10 mL deionized water, and a mixture of MIBK were added to a reactor (the volume ratio of deionized water to MIBK was 2:8). The mixture was stirred at 130 °C and 450 rpm for 10 h. After the reaction, the mixture was rapidly cooled to room temperature and centrifuged. After centrifugation, the reaction mixture separated into three layers: the upper layer was the organic phase containing the product, the middle layer was the aqueous phase, and the lower layer was the solid residue and catalyst. The solid residue and catalyst were placed in hot water at 80 °C, stirred, and filtered while hot. The filter residue was washed, dried, and weighed to calculate the conversion rate of holocellulose. The catalyst precipitated after the hot aqueous solution cooled to room temperature; the catalyst was washed, dried, and recycled.

[0055] Example 3

[0056] Preparation of alkaline DES: Lys and MEA in a molar ratio of 1:6 were mixed in a round-bottom flask and then stirred at 550 rpm in a constant-temperature magnetic stirring bath at 80°C until a homogeneous and transparent liquid was formed. The alkaline DES solvent was cooled to room temperature and stored in a desiccator for later use.

[0057] Preparation of larch holocellulose: 5g of larch raw material and 60g of alkaline DES solvent were mixed evenly in a round-bottom flask and stirred continuously at 110℃ and 550rpm for 7h. After the reaction was completed, the mixture was rapidly cooled to room temperature. The reaction mixture was separated into solid and liquid phases by vacuum filtration (pressure 0.5MPa). The filter residue was thoroughly washed with an acetone-water solution (acetone to water volume ratio 7:4) to remove residual DES solvent, and then washed with deionized water until neutral. The washed filter residue was collected and transferred to a vacuum drying oven (vacuum degree 0.05MPa) and dried at 85℃ to obtain larch holocellulose.

[0058] Temperature-controlled polyacid catalyst Ch3PW 12 O 40 Synthesis: Dissolve 3 mmol of choline chloride in 15 mL of deionized water and stir until the choline chloride is completely dissolved. Simultaneously, take 1 mmol of H3PW... 12 O 40 Dissolve in 20 mL of deionized water and stir until H3PW 12 O 40 Completely dissolve. Then, add choline chloride aqueous solution dropwise to H3PW at a rate of 10 mL / min. 12 O 40 In the aqueous solution, the mixture was stirred at room temperature for 13 hours, and then filtered to separate a white solid precipitate, which was washed three times with deionized water. The white solid precipitate was then dried in a vacuum drying oven (vacuum degree of 0.05 MPa) for 12 hours to obtain Ch3PW. 12 O 40 catalyst.

[0059] Preparation of furan chemicals: A mixture of 0.1 g holocellulose, 0.022 g AlCl3, 0.2 g catalyst, 10 mL deionized water, and MIBK (volume ratio of deionized water to MIBK 3:15) was added to a reactor and stirred at 170 °C and 550 rpm for 8 h. After the reaction, the mixture was rapidly cooled to room temperature and centrifuged. The reaction mixture separated into three layers after centrifugation: the upper layer was the organic phase containing the product, the middle layer was the aqueous phase, and the lower layer was the solid residue and catalyst. The solid residue and catalyst were placed in hot water at 85 °C, stirred, and filtered while hot. The filter residue was washed, dried, and weighed, and the conversion rate of holocellulose was calculated. The catalyst precipitated after the hot aqueous solution cooled to room temperature; the catalyst was washed, dried, and recycled.

[0060] SEM images of larch raw material and holocellulose in Example 1 are shown below. Figure 1 As shown, a and c are larch raw materials under different magnifications, and b and d are larch holocellulose under different magnifications;

[0061] The yield, conversion, and cycle performance of the temperature-controlled polyacid catalyst catalyzing the preparation of furan chemicals from holocellulose in Example 1 are as follows: Figure 2 As shown. By Figure 2 It can be seen that the dual-acid catalytic system composed of heteropolyacid and AlCl3 catalyzes the conversion of larch holocellulose into furan chemicals in a two-phase solvent composed of water and MIBK. Holocellulose is converted with high efficiency and the yields of HMF and FF are high. The aqueous solution of the polyacid catalyst and AlCl3 can be recycled and reused, and it still maintains high catalytic performance after five cycles.

[0062] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing furan chemicals from holocellulose, characterized in that, The process includes the following steps: reacting holocellulose, aluminum chloride, polyacid catalyst, water, and methyl isobutyl ketone to obtain furan chemicals; The preparation method of holocellulose includes the following steps: Lignocellulose raw material is reacted with a eutectic solvent at a temperature of 80-120 °C for 6-9 h to obtain holocellulose; The mass ratio of the lignocellulose raw material to the eutectic solvent is 2-6:60; the eutectic solvent is composed of lysine and ethanolamine, and the molar ratio of lysine to ethanolamine is 1:5-7. The polyacid catalyst is a temperature-controlled polyacid catalyst, and the chemical formula of the temperature-controlled polyacid catalyst is Ch. n H 3-n PW 12 O 40 , where n is 1, 2 or 3.

2. The method according to claim 1, characterized in that, In the preparation method of holocellulose, the reaction mixture obtained from the reaction is subjected to solid-liquid separation, and the filter residue after separation is washed and dried in sequence to obtain holocellulose.

3. The method according to claim 2, characterized in that, The washing reagents are, in order, acetone aqueous solution and water, wherein the volume ratio of acetone to water in the acetone aqueous solution is 6~8:2~4; the drying temperature is 70~90 ℃.

4. The method according to claim 3, characterized in that, The mass ratio of holocellulose, aluminum chloride and polyacid catalyst is 1:0.15~0.25:0~3; the volume ratio of water and methyl isobutyl ketone is 1~4:6~19.

5. The method according to claim 3 or 4, characterized in that, When holocellulose, aluminum chloride, polyacid catalyst, water and methyl isobutyl ketone are reacted, the reaction temperature is 120~170 ℃, the reaction time is 7~12 h, and the reaction is carried out under stirring conditions at a stirring rate of 400~600 rpm.

6. The method according to claim 5, characterized in that, The preparation method of the temperature-controlled polyacid catalyst is as follows: adding an aqueous solution of choline chloride dropwise to an aqueous solution of phosphotungstic acid to carry out the reaction, obtaining a solid precipitate, washing the solid precipitate and drying it to obtain the temperature-controlled polyacid catalyst; The molar ratio of choline chloride to phosphotungstic acid is 1~3:1; the concentration of the aqueous solution of choline chloride is 0.15~0.25 mol / L, and the concentration of the aqueous solution of phosphotungstic acid is 0.04~0.06 mol / L.

Images