A method for preparing pentosans

Abstract

This invention belongs to the field of pentosan preparation technology, specifically a method for preparing pentosan. Wheat bran powder undergoes a hydrothermal reaction in an aqueous barium acetate solution. Water extraction yields a supernatant and precipitate containing water-soluble pentosans. Sodium hydroxide and acetylacetone are then added, followed by alkaline extraction at 30-40°C to obtain a supernatant containing both water-soluble and alkali-soluble pentosans. This supernatant is then post-treated to obtain the pentosan product. This invention improves the extraction rate of water-soluble pentosans; the alkaline extraction effect is superior to that achieved using sodium hydroxide and barium hydroxide alone, and it reduces the amount of alkali solution, especially Ba(OH)₂, used.

Description

Technical Field

[0001] This invention belongs to the field of pentosan preparation technology, specifically a method for preparing pentosan. Background Technology

[0002] Hemicellulose is the most abundant biomass polymer, composed of β-D-xylanose (xylose) residues linked by β-1-4 glycosidic bonds. These glycosidic chains are tightly stacked together by hydrogen bonds and van der Waals forces, forming crystalline cellulose microfibers. Hemicellulose is among the most abundant biopolymer components found in wood and other plants such as grasses, cereals, and herbs.

[0003] Wheat bran contains a large amount of carbohydrates—hemicellulose. In the early 20th century, with in-depth research into wheat quality by the food chemistry community, it was discovered that besides proteins and starches significantly influencing the physical properties and quality of wheat, a non-obvious component with high content and viscosity also plays a crucial role in wheat quality. In 1927, Hoffmann et al. isolated this non-starch polysaccharide from wheat flour. Studies showed that this non-starch polysaccharide contains various pentoses, arabinose (L-Arabinose), and xylose (Xylan), and Hoffmann et al. named this polysaccharide pentosan. Pentosans can be classified into water-soluble and water-insoluble pentosans based on their solubility. Water-soluble pentosans have high solubility in water, while water-insoluble pentosans interact with components such as proteins, cellulose, and lignin in the cell wall through covalent or non-covalent bonds, forming a dense structure that is difficult to dissolve in water.

[0004] Cui Can et al. (Journal of Zhengzhou University of Light Industry (Natural Science Edition), Vol. 30, No. 1) used water and Ba(OH)2 as media to extract water-soluble and alkali-soluble pentosans from black wheat flour, respectively. In the extraction of alkali-soluble pentosans, large amounts of saturated Ba(OH)2 solution were added sequentially for extraction, which not only increased costs but also required further treatment of the alkali solution used. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing pentosans to overcome the defects mentioned in the background art.

[0006] According to a first aspect of the present invention, a method for preparing pentosan includes the following steps:

[0007] Step 1: Dry and grind the wheat bran, then sift it through a sieve to obtain powder;

[0008] Step 2: Add the powder to water and add barium acetate to obtain a first mixture. Then add the first mixture to a hydrothermal reactor and place the hydrothermal reactor at 70-90℃ for 2-4 hours. After the reaction is completed, let the mixture stand for 4-12 hours to obtain the intermediate product of Step 2.

[0009] Step 3: Add sodium hydroxide and acetylacetone to the intermediate product of step 2 to obtain a second mixture, and then react at 30-40℃ for 2-6 hours to obtain the product of step 3;

[0010] Step 4: The product from Step 3 is post-processed to obtain the final product, pentosan.

[0011] In one aspect of this invention, in step 1, the mesh size of the sieve is 40-100 mesh. Specifically, in step 1, the mesh size of the sieve is 80 mesh.

[0012] In one aspect of the present invention, step 1 includes: drying wheat bran at 60°C until its mass remains unchanged, and then pulverizing it through an 80-mesh sieve to obtain powder.

[0013] In one aspect of the present invention, in step 2, the mass ratio of the powder to water is 1:(8-12). Specifically, in step 2, the mass ratio of the powder to water is 1:10.

[0014] In one aspect of this invention, in step 2, the mass ratio of barium acetate to water is (0.5-3.5):100. Specifically, in step 2, the mass ratio of barium acetate to water is 2:100.

[0015] In one aspect of the invention, in step 3, the molar amount of acetylacetone added is 3-4 times the molar amount of barium acetate added in step 2. Specifically, in step 3, the molar amount of acetylacetone added is 3 times the molar amount of barium acetate added in step 2.

[0016] In one aspect of this invention, the concentration of sodium hydroxide in the second mixture is 0.2-0.3 mol / L. Specifically, the concentration of sodium hydroxide in the second mixture is 0.25 mol / L.

[0017] In one aspect of the present invention, in step 3, before adding sodium hydroxide and acetylacetone, a certain amount of water may be added as appropriate according to the actual situation.

[0018] In one aspect of the present invention, in step 4, the post-processing is as follows: after extraction and centrifugation of the intermediate product of step 2, the supernatant is collected; then the supernatant is washed, centrifuged, and anhydrous ethanol is added and allowed to stand for 3-10 hours, and the precipitate is collected; then the precipitate is freeze-dried to obtain the final product, the pentosan.

[0019] According to a second aspect of the present invention, a pentosan is a mixture of water-soluble pentosan and alkali-soluble pentosan, obtained by the aforementioned preparation method.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] (1) In the water extraction process, the present invention adds barium acetate to the water extraction solution and utilizes the selectivity of barium ions to improve the extraction rate of water-soluble pentosans compared with the prior art.

[0022] (2) In the alkaline extraction process, sodium hydroxide and acetylacetone are added to the alkaline extraction solution. Some of the acetylacetone forms a relatively stable complex with barium ions, which further increases the selectivity of barium ions in the alkaline extraction solution. In addition, acetylacetone has strong oxidizing properties, which can further hydrolyze polysaccharides and cell wall substances, intensify the release of polysaccharides, and accelerate the dissolution rate of polysaccharides. Its alkaline extraction effect is better than that of the alkaline extraction effect when sodium hydroxide and barium hydroxide are used alone in the prior art, and it can reduce the amount of alkaline solution, especially Ba(OH)2, used.

[0023] (3) The acetylacetone used in this invention forms a relatively stable complex with barium ions, which is easy to remove in post-processing.

[0024] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit the invention. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. The embodiments described herein are illustrative in nature and are intended to provide a basic understanding of this invention. The embodiments of this invention should not be construed as limiting the invention.

[0026] For the sake of brevity, this article only discloses a few specific numerical ranges. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, just as any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit and be combined with any other point or single value or with other lower or upper limits to form an unspecified range.

[0027] In this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0028] In this description, unless otherwise stated, "above" and "below" include the stated number.

[0029] Unless otherwise stated, the terminology used in this invention has the common meanings understood by those skilled in the art. Unless otherwise stated, the values ​​of the parameters mentioned in this invention can be measured using various measurement methods commonly used in the art (e.g., they can be tested according to the methods given in the embodiments of this invention).

[0030] The term "about" is used to describe and indicate small variations. When used in conjunction with an event or situation, the term may refer to examples in which the event or situation occurred precisely or in examples in which the event or situation occurred very approximately. For example, when used in conjunction with numerical values, the term may refer to a range of variation less than or equal to ±10% of the numerical value, such as less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to ±1%, less than or equal to ±0.5%, less than or equal to ±0.1%, or less than or equal to ±0.05%. Additionally, quantities, ratios, and other numerical values ​​are sometimes presented in range format herein. It should be understood that such range format is for convenience and brevity and should be interpreted flexibly to include not only numerical values ​​explicitly specified as range limits but also all individual numerical values ​​or subranges covered within the range, as if each numerical value and subrange were explicitly specified.

[0031] The list of items connected by the terms "at least one of," "at least one of," "at least one of," or other similar terms can mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" means only A; only B; or A and B. In another instance, if items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may contain a single component or multiple components. Item B may contain a single component or multiple components. Item C may contain a single component or multiple components.

[0032] The present invention will be further described below by way of specific embodiments. Unless otherwise specified, all chemical reagents used in the embodiments of the present invention were obtained through conventional commercial means. Unless otherwise specified, all contents mentioned below are mass contents. Unless otherwise specified, it is understood that the process was carried out at room temperature.

[0033] Example 1

[0034] Includes the following steps:

[0035] Wheat bran was dried at 60°C until its mass remained constant, and then pulverized through an 80-mesh sieve to obtain powder.

[0036] Weigh 10g of powder and add it to 100mL of deionized water. Then add 1.5g of barium acetate (5.87mmol) and add it to a hydrothermal reactor. Place the hydrothermal reactor at 80℃ and react for 3h. After the reaction is completed, let the mixture stand for 6h to obtain the supernatant and the precipitated intermediate product.

[0037] Add deionized water to the intermediate product to a final volume of 100 mL. Without separating the supernatant and precipitate, add 1 g of NaOH directly to prepare a 0.25 mol / L NaOH solution. Then add 1.17 g of acetylacetone (1.25 mL, 11.74 mmol) and react at 35 °C for 4 h. Take the supernatant.

[0038] After extracting the supernatant with ethyl acetate, centrifuge at 3000 r / min, collect the supernatant, wash with water and centrifuge again, mix the supernatants obtained from the two centrifugations, then add glacial acetic acid to adjust the pH to neutral, then add 120 mL of anhydrous ethanol, stir and let stand for 5 h, collect the precipitate, and then freeze-dry the precipitate to obtain the final product pentosan of Example 1.

[0039] Example 2

[0040] Includes the following steps:

[0041] Wheat bran was dried at 60°C until its mass remained constant, and then pulverized through an 80-mesh sieve to obtain powder.

[0042] Weigh 10g of powder and add it to 100mL of deionized water. Then add 1.5g of barium acetate (5.87mmol) and add it to a hydrothermal reactor. Place the hydrothermal reactor at 80℃ and react for 3h. After the reaction is completed, let the mixture stand for 6h to obtain the supernatant and the precipitated intermediate product.

[0043] Add deionized water to the intermediate product to a final volume of 100 mL. Without separating the supernatant and precipitate, add 1 g of NaOH directly to prepare a 0.25 mol / L NaOH solution. Then add 2.34 g of acetylacetone (2.50 mL, 23.48 mmol) and react at 35 °C for 4 h. Take the supernatant.

[0044] After extracting the supernatant with ethyl acetate, centrifuge at 3000 r / min, collect the supernatant, wash with water and centrifuge again, mix the supernatants obtained from the two centrifugations, then add glacial acetic acid to adjust the pH to neutral, then add 120 mL of anhydrous ethanol, stir and let stand for 5 h, collect the precipitate, and then freeze-dry the precipitate to obtain the final product pentosan of Example 2.

[0045] Example 3

[0046] Includes the following steps:

[0047] Wheat bran was dried at 60°C until its mass remained constant, and then pulverized through an 80-mesh sieve to obtain powder.

[0048] Weigh 10g of powder and add it to 100mL of deionized water. Then add 1.5g of barium acetate (5.87mmol) and add it to a hydrothermal reactor. Place the hydrothermal reactor at 80℃ and react for 3h. After the reaction is completed, let the mixture stand for 6h to obtain the supernatant and the precipitated intermediate product.

[0049] Add deionized water to the intermediate product to a final volume of 100 mL. Without separating the supernatant and precipitate, add 1 g of NaOH directly to prepare a 0.25 mol / L NaOH solution. Then add 4.68 g of acetylacetone (5 mL, 46.96 mmol) and react at 35 °C for 4 h. Take the supernatant.

[0050] After extracting the supernatant with ethyl acetate, centrifuge at 3000 r / min, collect the supernatant, wash with water and centrifuge again, mix the supernatants obtained from the two centrifugations, then add glacial acetic acid to adjust the pH to neutral, then add 120 mL of anhydrous ethanol, stir and let stand for 5 h, collect the precipitate, and then freeze-dry the precipitate to obtain the final product pentosan of Example 3.

[0051] Example 4

[0052] Includes the following steps:

[0053] Wheat bran was dried at 60°C until its mass remained constant, and then pulverized through an 80-mesh sieve to obtain powder.

[0054] Weigh 10g of powder and add it to 100mL of deionized water. Then add 1.5g of barium acetate (5.87mmol) and add it to a hydrothermal reactor. Place the hydrothermal reactor at 80℃ and react for 3h. After the reaction is completed, let the mixture stand for 6h to obtain the supernatant and the precipitated intermediate product.

[0055] Add deionized water to the intermediate product to a final volume of 100 mL. Without separating the supernatant and precipitate, add 1 g of NaOH directly to prepare a 0.25 mol / L NaOH solution. Add 0.585 g of acetylacetone (0.625 mL, 5.87 mmol) to the solution and react at 35 °C for 4 h. Take the supernatant.

[0056] After extracting the supernatant with ethyl acetate, centrifuge at 3000 r / min, collect the supernatant, wash with water and centrifuge again, mix the supernatants obtained from the two centrifugations, then add glacial acetic acid to adjust the pH to neutral, then add 120 mL of anhydrous ethanol, stir and let stand for 5 h, collect the precipitate, and then freeze-dry the precipitate to obtain the final product pentosan of Example 4.

[0057] Comparative Example 1

[0058] Includes the following steps:

[0059] Wheat bran was dried at 60°C until its mass remained constant, and then pulverized through an 80-mesh sieve to obtain powder.

[0060] Weigh 10g of powder and add it to 100mL of deionized water. Add the powder to a hydrothermal reactor and place the reactor at 80℃ for 3 hours. After the reaction is complete, let the mixture stand for 6 hours to obtain the supernatant and the precipitated intermediate product.

[0061] Add deionized water to the intermediate product to a final volume of 100 mL. Without separating the supernatant and precipitate, add 1 g of NaOH directly to prepare a 0.25 mol / L NaOH solution. Then, react the solution at 35 °C for 4 h and collect the supernatant.

[0062] Centrifuge the supernatant at 3000 r / min, take the supernatant, wash with water and centrifuge again, mix the supernatants obtained from the two centrifugations, then add glacial acetic acid to adjust the pH to neutral, then add 120 mL of anhydrous ethanol, stir and let stand for 5 h, collect the precipitate, and then freeze-dry the precipitate to obtain the final product pentosan of Comparative Example 1.

[0063] Comparative Example 2

[0064] Includes the following steps:

[0065] Wheat bran was dried at 60°C until its mass remained constant, and then pulverized through an 80-mesh sieve to obtain powder.

[0066] Weigh 10g of powder and add it to 100mL of deionized water. Then add 1.5g of barium acetate (5.87mmol) and add it to a hydrothermal reactor. Place the hydrothermal reactor at 80℃ and react for 3h. After the reaction is completed, let the mixture stand for 6h to obtain the supernatant and the precipitated intermediate product.

[0067] Add deionized water to the intermediate product to a final volume of 100 mL. Without separating the supernatant and precipitate, add 1 g of NaOH directly to prepare a 0.25 mol / L NaOH solution. Then, react the solution at 35 °C for 4 h and collect the supernatant.

[0068] After extracting the supernatant with ethyl acetate, centrifuge at 3000 r / min, collect the supernatant, wash with water and centrifuge again, mix the supernatants obtained from the two centrifugations, then add glacial acetic acid to adjust the pH to neutral, then add 120 mL of anhydrous ethanol, stir and let stand for 5 h, collect the precipitate, and then freeze-dry the precipitate to obtain the final product pentosan of Comparative Example 2.

[0069] The yields of intermediate and final products after hydrothermal reactions in Examples 1 to 4 and Comparative Examples 1 and 2 were calculated respectively. The calculation method was the mass of the extract / the mass of the raw material. The results are shown in the table below:

[0070] Example Yield of intermediate products after hydrothermal reaction Yield of final product Example 1 0.64 0.85 Example 2 0.65 0.97 Example 3 0.64 0.98 Example 4 0.63 0.77 Comparative Example 1 0.41 0.47 Comparative Example 2 0.65 0.73

[0071] Other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the disclosure herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein.

Claims

1. A method for preparing pentosan, characterized in that, Includes the following steps: Step 1: Dry and grind the wheat bran, then sift it through a sieve to obtain powder; Step 2: Add the powder to water and add barium acetate to obtain a first mixture. Then add the first mixture to a hydrothermal reactor and place the hydrothermal reactor at 70-90℃ for 2-4 hours. After the reaction is completed, let the mixture stand for 4-12 hours to obtain the intermediate product of Step 2. Step 3: Add sodium hydroxide and acetylacetone to the intermediate product of step 2 to obtain a second mixture, and then react at 30-40℃ for 2-6 hours to obtain the product of step 3; Step 4: The product from Step 3 is post-processed to obtain the final product, pentosan; In step 3, the molar amount of acetylacetone added is 3-4 times the molar amount of barium acetate added in step 2.

2. The method for preparing pentosan according to claim 1, characterized in that, In step 1, the mesh size of the sieve is 40-100 mesh.

3. The method for preparing pentosan according to claim 1, characterized in that, In step 2, the mass ratio of the powder to water is 1:(8-12).

4. The method for preparing pentosan according to claim 1, characterized in that, In step 2, the mass ratio of barium acetate to water is (0.5-3.5):

1.

5. The method for preparing pentosan according to claim 1, characterized in that, In the second mixture, the concentration of sodium hydroxide is 0.2-0.3 mol / L.