Preparation method of pentosan

Abstract

The invention belongs to the technical field of pentosan preparation, and particularly relates to a pentosan preparation method which comprises the following steps: performing hydrothermal reaction on wheat bran powder in an aqueous solution of barium acetate, and performing water extraction to obtain supernate containing water-soluble pentosan and precipitate; then adding sodium hydroxide and acetylacetone into the mixed solution, and carrying out alkali extraction at 30-40 DEG C to obtain supernate containing water-soluble pentosan and alkali-soluble pentosan; and carrying out post-treatment on the supernate to obtain a product pentosan. According to the method, the extraction rate of the water-soluble pentosan is increased; meanwhile, the alkali extraction effect is better than that when sodium hydroxide and barium hydroxide are independently used, and the use amount of alkali liquor, especially Ba (OH) 2, can be reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of pentosan preparation, and specifically relates to a method for preparing pentosan. Background Art

[0002] Hemicellulose is the most abundant biomass polymer and is composed of β-D-xylopyranosyl (xylose) residues linked by β-1-4 glycosidic bonds that are tightly stacked together by hydrogen bonds and van der Waals forces to form crystalline cellulose microfibrils. 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 carbohydrate-hemicellulose. In the early 20th century, as the grain chemistry community conducted in-depth research on wheat quality, it was found that in addition to protein and starch in wheat, which have an important impact on the physical properties and quality of wheat itself, a non-obvious component with a large content and high viscosity also plays a very important role in the quality of wheat itself. In 1927, Hoffman and others separated this non-starch polysaccharide from wheat flour. Studies have shown that this non-starch polysaccharide contains a variety of pentoses, arabinose (L-Arabinose) and xylose (Xylan). Hoffman and others named this polysaccharide pentosan. Pentosan can be divided into water-soluble and water-insoluble pentosans according to solubility. Water-soluble pentosans have a high solubility in water, and water-insoluble pentosans interact with components such as protein, cellulose and lignin in the cell wall in the form of covalent bonds or non-covalent bonds to form a dense tissue structure that is difficult to dissolve in water.

[0004] Cui Can et al. (Journal of Zhengzhou Institute of Light Industry (Natural Science Edition), Vol. 30, No. 1) used water and Ba(OH)2 as media to extract water-soluble pentosan and alkali-soluble pentosan from black wheat flour. When extracting alkali-soluble pentosan, a large amount of saturated Ba(OH)2 solution was added for leaching, which not only increased the cost, but also required further treatment of the alkali solution used. Summary of the invention

[0005] The object of the present invention is to provide a method for preparing pentosan to solve the defects pointed out in the above background technology.

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

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

[0008] Step 2: adding the powder to water and adding barium acetate to obtain a first mixed solution, then adding the first mixed solution to a hydrothermal reactor, placing the hydrothermal reactor at 70-90° C. for reaction for 2-4 hours; after the reaction is completed, allowing the reaction mixture to stand for 4-12 hours to obtain an intermediate product of step 2;

[0009] Step 3: adding sodium hydroxide and acetylacetone to the intermediate product of step 2 to obtain a second mixed solution, and then reacting at 30-40° C. for 2-6 hours to obtain the product of step 3;

[0010] Step 4: The product of step 3 is post-treated to obtain the final product, the pentosan.

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

[0012] In one aspect of the present invention, step 1 comprises: drying the wheat bran at 60° C. until the mass remains unchanged, and then crushing the wheat bran 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 the present 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 present 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 the present invention, in the second mixed solution, the concentration of sodium hydroxide is 0.2-0.3 mol / L. Specifically, in the second mixed solution, the concentration of sodium hydroxide 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 can be appropriately added according to actual conditions.

[0018] In one aspect of the present invention, in step 4, the post-treatment is: extracting and centrifuging the intermediate product of step 2, taking the supernatant; then washing and centrifuging the supernatant, adding anhydrous ethanol and standing for 3-10 hours, collecting the precipitate; and then freeze-drying the precipitate to obtain the final product, the pentosan.

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

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

[0021] (1) During 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) During the alkaline extraction process, sodium hydroxide and acetylacetone are added to the alkaline extraction solution. Part of the acetylacetone forms a relatively stable complex with the barium ion, which further increases the selectivity of the barium ion in the alkaline extraction solution. In addition, acetylacetone has strong oxidizing properties and can further hydrolyze the polysaccharides and cell wall substances, thereby intensifying the release of polysaccharides and accelerating the dissolution rate of polysaccharides. The alkaline extraction effect is better than the alkaline extraction effect when sodium hydroxide and barium hydroxide are used alone in the prior art, and the amount of alkaline solution, especially Ba(OH)2, can be reduced.

[0023] (3) The acetylacetone used in the present invention forms a relatively stable complex with the barium ion, which is easy to remove in post-treatment.

[0024] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. The relevant embodiments described herein are illustrative and are used to provide a basic understanding of the present invention. The embodiments of the present invention should not be interpreted as limiting the present invention.

[0026] For simplicity, only some numerical ranges are specifically disclosed herein. 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, and any upper limit can be combined with any other upper limit to form an unspecified range. In addition, each separately disclosed point or single value can itself be combined as a lower limit or upper limit with any other point or single value or with other lower limits or upper limits to form an unspecified range.

[0027] In this article, the terms "comprises", "comprising" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device that includes a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of more restrictions, an element defined by the sentence "comprising a ..." does not exclude the presence of other identical elements in the process, method, article or device that includes the element.

[0028] In the description herein, unless otherwise specified, “above” and “below” include the number.

[0029] Unless otherwise specified, the terms used in the present invention have the commonly known meanings generally understood by those skilled in the art. Unless otherwise specified, the numerical values ​​of the various parameters mentioned in the present invention can be measured using various measurement methods commonly used in the art (for example, they can be tested according to the methods given in the embodiments of the present invention).

[0030] The term "about" is used to describe and illustrate small changes. When used in conjunction with an event or situation, the term may refer to an example in which the event or situation occurs precisely and an example in which the event or situation occurs very approximately. For example, when used in conjunction with a numerical value, the term may refer to a range of variation of 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%. In addition, amounts, ratios, and other numerical values ​​are sometimes presented in this article in a range format. It should be understood that such a range format is for convenience and simplicity, and should be flexibly understood to include not only numerical values ​​explicitly designated as range limits, but also all individual numerical values ​​or subranges encompassed within the range, as if each numerical value and subrange were explicitly designated.

[0031] A list of items connected by the terms "at least one of," "at least one of," "at least one of," or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, 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 is further described below by way of specific examples. The various chemical reagents used in the examples of the present invention are obtained through conventional commercial channels unless otherwise specified. Unless otherwise specified, the contents described below are all weight contents. Unless otherwise specified, it is understood that the process is carried out at room temperature.

[0033] Embodiment 1

[0034] The following steps are involved:

[0035] The wheat bran was dried at 60°C until the mass remained unchanged, and then crushed through an 80-mesh sieve to obtain a powder;

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

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

[0038] The supernatant was extracted with ethyl acetate and centrifuged at 3000 r / min. The supernatant was taken, washed with water and centrifuged again. The supernatants obtained from the two centrifugations were mixed, and then glacial acetic acid was added to adjust the pH value to neutral. Then 120 mL of anhydrous ethanol was added, and the mixture was allowed to stand for 5 h after stirring. The precipitate was collected and then freeze-dried to obtain the final product pentosan of Example 1.

[0039] Embodiment 2

[0040] The following steps are involved:

[0041] The wheat bran was dried at 60°C until the mass remained unchanged, and then crushed through an 80-mesh sieve to obtain a powder;

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

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

[0044] The supernatant was extracted with ethyl acetate and centrifuged at 3000 r / min. The supernatant was taken, washed with water and centrifuged again. The supernatants obtained from the two centrifugations were mixed, and then glacial acetic acid was added to adjust the pH value to neutral. Then 120 mL of anhydrous ethanol was added, and the mixture was allowed to stand for 5 hours after stirring. The precipitate was collected and then freeze-dried to obtain the final product of Example 2, pentosan.

[0045] Embodiment 3

[0046] The following steps are involved:

[0047] The wheat bran was dried at 60°C until the mass remained unchanged, and then crushed through an 80-mesh sieve to obtain a powder;

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

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

[0050] The supernatant was extracted with ethyl acetate and centrifuged at 3000 r / min. The supernatant was taken, washed with water and centrifuged again. The supernatants obtained from the two centrifugations were mixed, and then glacial acetic acid was added to adjust the pH value to neutral. Then 120 mL of anhydrous ethanol was added, and the mixture was allowed to stand for 5 hours after stirring. The precipitate was collected and then freeze-dried to obtain the final product pentosan of Example 3.

[0051] Embodiment 4

[0052] The following steps are involved:

[0053] The wheat bran was dried at 60°C until the mass remained unchanged, and then crushed through an 80-mesh sieve to obtain a powder;

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

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

[0056] The supernatant was extracted with ethyl acetate and centrifuged at 3000 r / min. The supernatant was taken, washed with water and centrifuged again. The supernatants obtained from the two centrifugations were mixed, and then glacial acetic acid was added to adjust the pH value to neutral. Then 120 mL of anhydrous ethanol was added, and the mixture was allowed to stand for 5 hours after stirring. The precipitate was collected and then freeze-dried to obtain the final product pentosan of Example 4.

[0057] Comparative Example 1

[0058] The following steps are involved:

[0059] The wheat bran was dried at 60°C until the mass remained unchanged, and then crushed through an 80-mesh sieve to obtain a powder;

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

[0061] Deionized water was added to the intermediate product to 100 mL, and 1 g of NaOH was directly added thereto without separating the supernatant and the precipitate to prepare a 0.25 mol / L NaOH solution, and then the reaction was carried out at 35° C. for 4 h, and the supernatant was taken.

[0062] The supernatant was centrifuged at 3000 r / min, the supernatant was taken, washed with water and centrifuged again, the supernatants obtained from the two centrifugations were mixed, and then glacial acetic acid was added to adjust the pH value to neutral, and then 120 mL of anhydrous ethanol was added. After stirring, it was allowed to stand for 5 hours, the precipitate was collected, and then the precipitate was freeze-dried to obtain the final product pentosan of Comparative Example 1.

[0063] Comparative Example 2

[0064] The following steps are involved:

[0065] The wheat bran was dried at 60°C until the mass remained unchanged, and then crushed through an 80-mesh sieve to obtain a powder;

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

[0067] Deionized water was added to the intermediate product to 100 mL, and 1 g of NaOH was directly added thereto without separating the supernatant and the precipitate to prepare a 0.25 mol / L NaOH solution, and then the reaction was carried out at 35° C. for 4 h, and the supernatant was taken.

[0068] The supernatant was extracted with ethyl acetate and centrifuged at 3000 r / min. The supernatant was taken, washed with water and centrifuged again. The supernatants obtained from the two centrifugations were mixed, and then glacial acetic acid was added to adjust the pH value to neutral. Then 120 mL of anhydrous ethanol was added, and the mixture was allowed to stand for 5 hours after stirring. The precipitate was collected and then freeze-dried to obtain the final product of pentosan in Comparative Example 2.

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

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

[0071] Those skilled in the art will readily appreciate other embodiments of the present invention after considering the specification and practicing the disclosure disclosed herein. The present invention is intended to cover any variations, uses or adaptations of the present invention that follow the general principles of the present invention and include common knowledge or customary technical means in the art that are not disclosed by the present invention.

Claims

1. A method for preparing pentosan, characterized in that: The following steps are involved: Step 1: drying and crushing the wheat bran, and then crushing it through a sieve to obtain powder; Step 2: adding the powder to water and adding barium acetate to obtain a first mixed solution, then adding the first mixed solution to a hydrothermal reactor, placing the hydrothermal reactor at 70-90° C. for reaction for 2-4 hours; after the reaction is completed, allowing the reaction mixture to stand for 4-12 hours to obtain an intermediate product of step 2; Step 3: adding sodium hydroxide and acetylacetone to the intermediate product of step 2 to obtain a second mixed solution, and then reacting at 30-40° C. for 2-6 hours to obtain the product of step 3; Step 4: The product of step 3 is post-treated to obtain the final product, the pentosan.

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 meshes.

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 step 3, the molar amount of acetylacetone added is 3-4 times the molar amount of barium acetate added in step 2.

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

7. The method for preparing pentosan according to claim 1, characterized in that: In step 4, the post-treatment is as follows: extracting and centrifuging the intermediate product of step 2, taking the supernatant; then washing and centrifuging the supernatant, adding anhydrous ethanol and standing for 3-10 hours, collecting the precipitate; and then freeze-drying the precipitate to obtain the final product, the pentosan.

8. A pentosan, which is a mixture of water-soluble pentosan and alkali-soluble pentosan, characterized in that: The pentosan is obtained by the preparation method of any one of claims 1 to 7.