Method for co-production of xylooligosaccharide and bio-based polyol by hydrothermal pretreatment-thermochemical liquefaction of straw
Through the hydrothermal pretreatment and thermal chemical liquefaction methods of straw, the straw structure is destroyed, the liquefaction efficiency is improved, and high-purity oligopolyses and bio-based polyols are prepared, which solves the problem of low straw utilization and achieves low-cost, environmentally friendly and efficient conversion.
Patent Information
- Application Number
- CN202510449678.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-11
- Publication Date
- 2025-07-18
AI Technical Summary
The existing straw pretreatment methods have problems such as complex operation, high cost, high environmental risks and difficult to efficiently utilize. Especially when preparing bio-based polyols and xylosol, the existing methods are difficult to destroy the dense structure of the straw, resulting in low liquefaction efficiency.
The dense skeleton structure of the straw is destroyed by hydrothermal pretreatment and increased porosity by hydrothermal pretreatment. The hydrothermal solution is treated with a fixed bed separator to prepare oligomer xylosol. At the same time, the hydrothermal pretreatment slag is converted into liquid polyol under acid catalysis using polyol as liquefied solvent.
It achieves efficient liquefaction of straw, improves the yield of xylooligosaccharides and bio-based polyols, reduces operating costs, and is environmentally friendly, does not produce harmful waste, and meets the requirements of sustainable development.
Smart Images
Figure CN120329360A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of biochemistry, and particularly relates to a method for co-producing xylo-oligosaccharide and bio-based polyols by hydrothermal pretreatment-thermochemical liquefaction of straw. Background Art
[0002] Green building materials refer to those clean, energy-saving, and green materials used in construction projects, which can reduce the use of natural energy and resources and have the advantages of energy conservation and consumption reduction, safety and non-toxicity, etc. Polyurethane foam, as a new type of green building material, has good heat insulation and impact resistance, etc.
[0003] At present, there are mainly two major problems with polyurethane foam as a thermal insulation building material: one is that the raw materials for synthesizing polyurethane (petroleum-based polyols and isocyanates) mostly come from fossil resources, resulting in high costs. The other is that petroleum-based polyurethane materials are not easily degraded in the natural environment. The key to solving these two problems lies in finding a renewable bio-based chemical to replace petroleum-based polyols to synthesize degradable polyurethane materials.
[0004] The synthesis of polyurethane materials using vegetable oil polyols such as soybean oil polyols as raw materials has been industrialized. However, since the raw material of vegetable oil polyols is vegetable oil, there is a problem of competing with the people for food. Therefore, it is of great practical significance to prepare bio-based chemicals such as bio-based polyols from lignocellulosic resources such as straw with huge reserves and renewability.
[0005] Crop straw is a typical agricultural waste and an important biomass. Straw is mainly composed of cellulose (40% - 50%), hemicellulose (20% - 35%), and lignin (20% - 40%). These components all contain abundant hydroxyl groups, making it a promising raw material for producing bio-based polyols. However, the straw structure is complex. Cellulose is embedded in an orderly fiber bundle in a network structure tightly bound by lignin and hemicellulose through hydrogen bonds. At the same time, cellulose serves as the framework structure of the network structure, while lignin and hemicellulose serve as connecting substances, filling the gaps in cellulose and jointly forming this complex network structure. Therefore, due to the natural physical barrier of lignocellulose, it is difficult to be decomposed by liquefaction solvents, resulting in low straw utilization rate.
[0006] To achieve the full-component utilization of wheat straw, certain means need to be adopted for its pretreatment. Many pretreatment means have been developed so far, mainly including chemical, physical, biological methods, etc. Chemical methods mainly include alkali / acid pretreatment, organic solution pretreatment, ionic liquid pretreatment, etc. Although the effects are remarkable, the operations are complex, the environmental risks are high, and the cost investment is large. Physical pretreatment methods mainly include ball milling, microwave, and steam explosion, etc. These methods are relatively easy to damage the cell wall and surface wax layer of straw, but these methods have problems such as small output, large equipment investment, complex operation, and high investment cost. Therefore, it is urgent to explore an efficient pretreatment method for lignocellulose such as straw. Summary of the Invention
[0007] The object of the present invention is to provide a method for co-producing xylooligosaccharide and bio-based polyol by hydrothermal pretreatment-thermochemical liquefaction of straw, which has simple operation, low cost investment, is environmentally friendly, and has remarkable effects.
[0008] The present invention is realized through the following technical solutions: A method for co-producing xylooligosaccharide and bio-based polyol by hydrothermal pretreatment-thermochemical liquefaction of straw. Through hydrothermal pretreatment of straw and adopting a thermochemical liquefaction process, the solid hydrothermal pretreatment residue is converted into a liquid bio-based polyol. At the same time, a fixed-bed separator is used to adsorb and elute the hydrothermal solution to obtain a xylooligosaccharide solution with different degrees of polymerization. The collected xylooligosaccharide solution is concentrated and freeze-dried to obtain a high-purity xylooligosaccharide product. This method includes the following steps: (1) Hydrothermal pretreatment: Place the crushed and dried straw in a reactor, add a certain amount of water, and conduct a hydrothermal reaction; after the reaction ends, separate the solid and liquid to obtain a hydrothermal solution rich in xylooligosaccharide and a hydrothermal pretreatment residue. (2) Preparation of xylooligosaccharide product: The hydrothermal solution obtained in step (1) is enriched by using a resin fixed-bed column, then eluted with an organic solvent, and successively concentrated and freeze-dried to obtain a xylooligosaccharide product. (3) Thermochemical liquefaction: Dry the hydrothermal pretreatment residue obtained in step (1); place the dried hydrothermal pretreatment residue in a reactor, use polyol as a liquefaction solvent, and under the catalytic action of an acid, liquefy the hydrothermal pretreatment residue to convert it into a liquid liquefied polyol.
[0009] In step (1), the straw is one of wheat straw, corn straw, or bagasse.
[0010] In step (1), the hydrothermal pretreatment conditions are: the solid-liquid ratio of straw to water is 1:2-5, the reaction temperature is 150°C-200°C, and the reaction time is 1h-5h.
[0011] In step (2), the preparation conditions of xylooligosaccharide product are as follows: the resin fixed bed column is one of activated carbon or macroporous adsorption resin, the organic solvent is one of methanol or ethanol, the eluent is first concentrated by vacuum distillation, and then freeze-dried to obtain xylooligosaccharide powder.
[0012] In step (3), the drying conditions of the hydrothermally pretreated residue are: drying at 80 - 105 °C for 6 - 12 hours.
[0013] In step (3), the liquefaction solvent polyol is one of polyethylene glycol 400, ethylene glycol, and glycerol.
[0014] In step (3), the solid-liquid ratio of the dried hydrothermally pretreated residue to the polyol is 1 / 3 - 1 / 5.
[0015] In step (3), the acid is one of sulfuric acid and hydrochloric acid; the mass fraction of the acid is 2% - 5% of the polyol.
[0016] In step (3), the liquefaction conditions are: liquefaction temperature 140 - 180 °C, liquefaction time 1 - 3 h.
[0017] Compared with the existing technology, the technical solution of the present invention has the following advantages: 1. Hydrothermal pretreatment destroys the dense skeletal structure of straw, increases its surface porosity, thus facilitating the contact between straw and liquefaction solvent and improving the liquefaction efficiency. At the same time, after pretreatment, the dosage of glycerol in the liquefaction solvent can be significantly increased on the premise of ensuring liquefaction efficiency, thereby reducing the liquefaction cost.
[0018] 2. Hydrothermal pretreatment can effectively degrade hemicellulose in straw to generate xylooligosaccharide with prebiotic activity, so as to realize the high-value utilization of straw.
[0019] 3. Hydrothermal pretreatment does not require the addition of a catalyst, hardly corrodes the equipment, and no harmful waste is generated during the treatment process. It is environmentally friendly and meets the requirements of sustainable development. These advantages make hydrothermal pretreatment an important pretreatment method for straw utilization and have broad application prospects. Description of the Drawings
[0020] Figure 1 SEM photos of wheat straw (left) and hydrothermally pretreated residue (right). Detailed Embodiments
[0021] The following further illustrates the technical solution of the present invention in conjunction with embodiments, but it should not be construed as a limitation to the present invention.
[0022] Example 1: Co-production of xylooligosaccharide and bio-based polyol according to the following steps (1) Hydrothermal pretreatment: 5000 g of pulverized and dried wheat straw was placed in a reactor, a certain amount of water was added, and hydrothermal reaction was carried out; after the reaction ended, solid-liquid separation was performed to obtain a hydrothermal solution rich in xylooligosaccharides and hydrothermal pretreatment residue; the hydrothermal pretreatment conditions were: the solid-liquid ratio of straw to water was 1:2, the reaction temperature was 150 °C, and the reaction time was 1 h; (2) Preparation of xylooligosaccharide product: The hydrothermal solution obtained in step (1) was enriched using an activated carbon-packed fixed bed column, then eluted with ethanol, and the ethanol eluate was collected and subjected to vacuum distillation and freeze-drying to obtain a xylooligosaccharide product; based on the xylan content in the raw material, the yield of xylooligosaccharides was 43.58%, and the purity > 98%; (3) Thermochemical liquefaction: The hydrothermal pretreatment residue obtained in step (1) was dried at 80 °C for 12 hours; 3000 g of the dried hydrothermal pretreatment residue was placed in a reactor, and polyol was used as the liquefaction solvent. Under the catalytic action of an acid, the hydrothermal pretreatment residue was liquefied to be converted into a liquid liquefied polyol; the liquefaction solvent polyol was polyethylene glycol 400, and the solid-liquid ratio of the dried hydrothermal pretreatment residue to polyol was 1 / 3; the acid was sulfuric acid, and the mass fraction of the acid was 2% of the polyol; the liquefaction conditions were: the liquefaction temperature was 140 °C, and the liquefaction time was 3 h; a certain amount of bio-based polyol was fully dissolved with 5 times of dioxane / water mixture, and the conversion rate of the hydrothermal pretreatment residue was measured to be 89.78%, and the hydroxyl value of the bio-based polyol was 694.09 mgKOH / g.
[0023] Example 2: Co-production of xylooligosaccharides and bio-based polyols according to the following steps (1) Hydrothermal pretreatment: 5000 g of pulverized and dried corn straw was placed in a reactor, a certain amount of water was added, and hydrothermal reaction was carried out; after the reaction ended, solid-liquid separation was performed to obtain a hydrothermal solution rich in xylooligosaccharides and hydrothermal pretreatment residue; the hydrothermal pretreatment conditions were: the solid-liquid ratio of straw to water was 1:3.5, the reaction temperature was 175 °C, and the reaction time was 3 h; (2) Preparation of xylooligosaccharide product: The hydrothermal solution obtained in step (1) was enriched using an activated carbon-packed fixed bed column, then eluted with ethanol, and the ethanol eluate was collected and subjected to vacuum distillation and freeze-drying to obtain a xylooligosaccharide product; based on the xylan content in the raw material, the yield of xylooligosaccharides was 43.58%, and the purity > 98%; (3) Thermochemical liquefaction: The hydrothermal pretreatment residue obtained in the step (1) is dried at 105 °C for 6 hours; 3000 g of the dried hydrothermal pretreatment residue is placed in a reactor, and polyol is used as the liquefaction solvent. Under the catalytic action of an acid, the hydrothermal pretreatment residue is liquefied to be converted into a liquid liquefied polyol; the liquefaction solvent polyol is ethylene glycol, and the solid-liquid ratio of the dried hydrothermal pretreatment residue to the polyol is 1 / 4; the acid is hydrochloric acid, and the mass fraction of the acid is 3.5% of the polyol; the liquefaction conditions are: liquefaction temperature 160 °C, liquefaction time 2 h; A certain amount of bio-based polyol is fully dissolved with 5 times of dioxane / water mixture, and the conversion rate of the hydrothermal pretreatment residue is measured to be 75.78%, and the hydroxyl value of the bio-based polyol is 116.47 mg KOH / g.
[0024] Example 3: Co-production of xylooligosaccharides and bio-based polyols according to the following steps (1) Hydrothermal pretreatment: 5000 g of crushed and dried sugarcane bagasse is placed in a reactor, and a certain amount of water is added for hydrothermal reaction; after the reaction is completed, solid-liquid separation is carried out to obtain a hydrothermal solution rich in xylooligosaccharides and a hydrothermal pretreatment residue; the hydrothermal pretreatment conditions are: the solid-liquid ratio of straw to water is 1:5, the reaction temperature is 200 °C, and the reaction time is 5 h; (2) Preparation of xylooligosaccharide product: The hydrothermal solution obtained in the step (1) is enriched by using a fixed bed column filled with macroporous adsorption resin, and then eluted with methanol. The ethanol eluate is collected and subjected to vacuum distillation and freeze-drying to obtain a xylooligosaccharide product; based on the xylan content in the raw material, the yield of xylooligosaccharides is 33.58%, and the purity > 96%; (3) Thermochemical liquefaction: The hydrothermal pretreatment residue obtained in the step (1) is dried at 90 °C for 8 hours; 3000 g of the dried hydrothermal pretreatment residue is placed in a reactor, and polyol is used as the liquefaction solvent. Under the catalytic action of an acid, the hydrothermal pretreatment residue is liquefied to be converted into a liquid liquefied polyol; the liquefaction solvent polyol is glycerol, and the solid-liquid ratio of the dried hydrothermal pretreatment residue to the polyol is 1 / 5; the acid is sulfuric acid, and the mass fraction of the acid is 5% of the polyol; the liquefaction conditions are: liquefaction temperature 180 °C, liquefaction time 1 h; A certain amount of bio-based polyol is fully dissolved with 5 times of dioxane / water mixture, and the conversion rate of the hydrothermal pretreatment residue is measured to be 89.78%, and the hydroxyl value of the bio-based polyol is 694.09 mg KOH / g.
[0025] Example 4: Co-production of xylooligosaccharides and bio-based polyols according to the following steps (1) Hydrothermal pretreatment: Place 5000 g of pulverized and dried wheat straw in a reactor, add a certain amount of water, and conduct hydrothermal reaction; after the reaction is completed, separate the solid and liquid to obtain a hydrothermal solution rich in xylo-oligosaccharides and hydrothermal pretreatment residue; the hydrothermal pretreatment conditions are: the solid-liquid ratio of straw to water is 1:3, the reaction temperature is 190 °C, and the reaction time is 3 h; (2) Preparation of xylo-oligosaccharide product: The hydrothermal solution obtained in step (1) is enriched by using a macroporous adsorption resin fixed-bed column, and then eluted with ethanol. The ethanol eluate is collected and subjected to vacuum distillation and freeze-drying to obtain a xylo-oligosaccharide product; based on the xylan content in the raw material, the yield of xylo-oligosaccharide is 45.58%, and the purity > 97%; (3) Thermochemical liquefaction: Dry the hydrothermal pretreatment residue obtained in step (1) at 100 °C for 7 hours; place 3000 g of the dried hydrothermal pretreatment residue in a reactor, use polyol as the liquefaction solvent, and under the catalytic action of an acid, liquefy the hydrothermal pretreatment residue to convert it into a liquid liquefied polyol; the liquefaction solvent polyol is ethylene glycol and glycerol, and the solid-liquid ratio of the dried hydrothermal pretreatment residue to polyol is 1 / 4; the acid is hydrochloric acid, and the mass fraction of the acid is 4% of the polyol; the liquefaction conditions are: the liquefaction temperature is 150 °C, and the liquefaction time is 2.5 h; take a certain amount of bio-based polyol, fully dissolve it with 5 times the amount of dioxane / water mixture, and the conversion rate of the hydrothermal pretreatment residue is measured to be 95.74%, and the hydroxyl value of the bio-based polyol is 496.24 mgKOH / g.
[0026] Comparative example: Place 3000 g of dried wheat straw in a reactor, add 500 g of polyethylene glycol, 1000 g of glycerol, and 45 g of sulfuric acid, react at 170 °C for 2 h, and quickly cool it with an ice-water bath after the reaction is completed to obtain bio-based polyol; take a certain amount of bio-based polyol, fully dissolve it with 5 times the amount of dioxane / water mixture, and the conversion rate of the hydrothermal pretreatment residue is measured to be 71.26%, and the hydroxyl value of the bio-based polyol is 611.11 mg KOH / g.
[0027] It can be seen from the comparison between the comparative example and the examples that hydrothermal pretreatment significantly improves the liquefaction efficiency of straw.
[0028] The above detailed description is a specific description of the feasible embodiments of the present invention. This embodiment is not intended to limit the patent scope of the present invention. Any equivalent implementation or modification without departing from the present invention shall be included in the patent protection scope of this case.
Claims
1. Method for co-producing xylooligosaccharides and bio-based polyols by hydrothermal pretreatment-thermochemical liquefaction of straw, the method comprising the following steps: (1) Hydrothermal pretreatment: Place the crushed and dried straw in a reactor, add a certain amount of water, and conduct hydrothermal reaction; after the reaction ends, perform solid-liquid separation to obtain a hydrothermal solution rich in xylooligosaccharides and hydrothermal pretreatment residue; (2) Preparation of xylooligosaccharide product: The hydrothermal solution obtained in step (1) is enriched by a resin fixed bed column, then eluted with an organic solvent, and successively concentrated and freeze-dried to obtain a xylooligosaccharide product; (3) Thermochemical liquefaction: Dry the hydrothermal pretreatment residue obtained in step (1); place the dried hydrothermal pretreatment residue in a reactor, use a polyol as a liquefaction solvent, and under the catalytic action of an acid, liquefy the hydrothermal pretreatment residue to convert it into a liquid liquefied polyol.
2. The method for co-producing xylooligosaccharide and bio-based polyol by hydrothermal pretreatment-thermochemical liquefaction of straw according to claim 1, wherein The straw in step (1) is one of wheat straw, corn straw or sugarcane bagasse.
3. The method for co-producing xylo-oligosaccharides and bio-based polyols by hydrothermal pretreatment-thermochemical liquefaction of straw according to claim 1, wherein, The hydrothermal pretreatment conditions in step (1) are: the solid-liquid ratio of straw to water is 1:2 to 5, the reaction temperature is 150°C to 200°C, and the reaction time is 1 h to 5 h.
4. The method for co-producing xylo-oligosaccharides and bio-based polyols by hydrothermal pretreatment-thermochemical liquefaction of straw according to claim 1, characterized in that, The xylooligosaccharide product preparation conditions in step (2) are: the resin fixed bed column is one of activated carbon or macroporous adsorption resin, the organic solvent is one of methanol or ethanol, the eluate is first concentrated by vacuum distillation, and then freeze-dried to obtain xylooligosaccharide powder.
5. The method for co-producing xylo-oligosaccharide and bio-based polyol by hydrothermal pretreatment-thermochemical liquefaction of straw according to claim 1, wherein In step (3), the drying conditions of the hydrothermal pretreatment residue are: drying at 80 - 105°C for 6 - 12 hours.
6. The method for co-producing xylooligosaccharide and bio-based polyol by hydrothermal pretreatment-thermochemical liquefaction of straw according to claim 1, characterized in that, In step (3), the liquefaction solvent polyol is one of polyethylene glycol 400, ethylene glycol, and glycerol.
7. The method for co-producing xylo-oligosaccharide and bio-based polyol by hydrothermal pretreatment-thermochemical liquefaction of straw according to claim 1, wherein In step (3), the solid-liquid ratio of the dried hydrothermal pretreatment residue to the polyol is 1 / 3 to 1 / 5.
8. The method for co-producing xylo-oligosaccharide and bio-based polyol by hydrothermal pretreatment-thermochemical liquefaction of straw according to claim 1, characterized in that, In step (3), the acid is one of sulfuric acid and hydrochloric acid; the mass fraction of the acid is 2% to 5% of the polyol.
9. The method for co-producing xylo-oligosaccharides and bio-based polyols by hydrothermal pretreatment-thermochemical liquefaction of straw according to claim 1, wherein In step (3), the liquefaction conditions are: liquefaction temperature 140 - 180°C, liquefaction time 1 - 3 h.