Method for utilizing multiple components of camellia oleifera shells

Abstract

The invention relates to the technical field of waste resource reutilization, in particular to a method for utilizing multiple components of camellia oleifera shells, which specifically comprises the following steps: extracting and preparing tea saponin, tannin, fructo-oligosaccharide and lignosulfonate in the camellia oleifera shells; according to the method disclosed by the invention, the problem of multi-component and high-value utilization of the camellia oleifera shells is solved, technical process conditions are defined, separation and purification of various chemical components in the camellia oleifera shells are realized, and chemical products with high added values are prepared.

Description

[Technical field]

[0001] The invention relates to the technical field of waste resource recycling, and in particular to a method for utilizing multiple components of oil-tea camellia shells. [Background technology]

[0002] Camellia oleifera Abel is one of the four major woody edible oil trees along with olive, oil palm and coconut. It is mainly distributed in Hunan, Jiangxi, Guangxi and Guangdong in southern China. By 2022, the annual output of camellia oleifera fruit in China will reach 5.6 million tons. Camellia oleifera fruit consists of camellia seeds and husks, of which the husks account for 50-60% of the total mass of the fruit. However, due to the low-value processing technology, the biomass resources of camellia oleifera husks are wasted. Therefore, it is necessary to develop technologies for high-value utilization of camellia oleifera husks to achieve full utilization of biomass resources.

[0003] Camellia oleifera husks are rich in hemicellulose (20-35%) and lignin (30-36%), which can be used to produce high value-added products such as ethanol, xylose, xylitol, furfural, xylo-oligosaccharides (XOS), activated carbon, active electrode materials and lignin complexes. However, there are few reports on the high-value utilization of tea saponins (8-20%) and tannins (7-13%) in camellia oleifera husks.

[0004] So far, the utilization of camellia husks has mainly focused on the pyrolysis of hemicellulose, lignin and cellulose or the production of activated carbon. The components used are single, resulting in the waste of other chemical components.

[0005] Juntao Zhang et al. used ZnCl2 activation method to prepare cost-effective activated carbon from waste oil tea shell as active electrode material for electric double layer capacitors. Liping Zhang et al. used malic acid to hydrolyze oil tea shells under mild conditions to prepare oligoxylose and lignin. Wei Xu et al. used oil tea shells as raw materials to prepare oligoxylose (XOS) using shell-based solid acid (CFS-bsa).

[0006] At present, there is no technology to realize the multi-component utilization of oil-tea camellia shells, and the present invention arises at the historic moment. [Summary of the invention]

[0007] In view of the above, it is necessary to provide a method for multi-component utilization of camellia oleifera shells to solve the problem of multi-component and high-value utilization of camellia oleifera shells, clarify the technical process conditions, realize the separation and purification of various chemical components in camellia oleifera shells, and prepare high value-added chemical products.

[0008] In order to achieve the above object, the technical solution adopted by the present invention is:

[0009] A method for utilizing multiple components of camellia oleifera shells, the method comprising the following steps:

[0010] (1) Pretreatment: Mixing the camellia oleifera shell with water, followed by extraction under ultrasonic conditions to obtain an extract concentrate, drying the extract concentrate to obtain a crude extract for later use, and naturally air-drying the camellia oleifera fruit residue obtained after the extraction to obtain a residue A for later use;

[0011] (2) Extracting tea saponin and tannin: adding water to the crude extract, then adding n-butanol to the resulting solution and stirring for 0.5-1.5 hours, then standing to separate the liquids; concentrating and drying the supernatant to obtain tea saponin, and concentrating and drying the lower supernatant to obtain tannic acid;

[0012] (3) Extracting xylo-oligosaccharides: adding 0.5-1.5% formic acid to the residue A, and then reacting in a reactor for 15-25 minutes. After the reaction is completed, the reactor is placed in water to cool, and then the reactants in the reactor are filtered and separated to obtain an extract and a residue. The residue is rinsed with deionized water until neutral, air-dried, and a residue B is obtained for later use; the extract is concentrated under reduced pressure, and then ethanol is added, stirred and mixed, and then allowed to stand until the xylo-oligosaccharides are precipitated, the supernatant is absorbed, and the ethanol is recovered by distillation under reduced pressure. The precipitate is dried to obtain xylo-oligosaccharides;

[0013] (4) Preparation of sodium lignin sulfonate: Residue B is placed in a reactor, sodium hydroxide solution is added, and then sodium 3-chloro-2-hydroxypropanesulfonate is added to react; after the reaction, the reactor is immersed in water until the mixture therein is cooled to room temperature, and then the pH of the mixture is adjusted to 6.5-7.5 with HCl solution, and the mixture is transferred to a membrane dialysis bag (1000 g / mol), dialyzed in distilled water, and the dialyzate is dried to obtain the final sulfonated lignin product.

[0014] Furthermore, in the step (1), the solid-liquid ratio of camellia oleifera shell to water is 1:25-35, the ultrasonic extraction temperature is 45-55° C., and the ultrasonic extraction time is 15-25 min.

[0015] Furthermore, in step (1), the solid-liquid ratio of camellia oleifera shell to water is 1:30, the ultrasonic extraction temperature is 50° C., and the ultrasonic extraction time is 20 min.

[0016] Furthermore, water is added to the crude extract in step (2) to make the concentration of the resulting solution 0.5-1.5 g / L.

[0017] Furthermore, in step (2), the volume ratio of the solution to n-butanol is 2:1.

[0018] Furthermore, in step (3), the material-liquid ratio of the residue A to formic acid is 1:9-12.

[0019] Furthermore, the extract in step (3) is concentrated under reduced pressure to 1 / 3 of the original volume, and then ethanol in an amount three times the volume of the concentrate is added, stirred for 4-6 minutes, and allowed to stand for 3.5-4.5 hours to allow the xylooligosaccharide to precipitate.

[0020] Furthermore, the reaction temperature of the reactor in step (3) is 160°C.

[0021] Furthermore, in the step (4), the amount of sodium 3-chloro-2-hydroxypropanesulfonate added is 9-12% of the mass of the residue B, and the stirring reaction of sodium 3-chloro-2-hydroxypropanesulfonate is specifically carried out at a speed of 380-420 rpm for 1-4 hours, and the reaction temperature is 100°C.

[0022] Furthermore, in the step (4), the membrane dialysis bag has a molecular weight cutoff of 900-1100 g / mol, and the dialysis is performed in distilled water for 48 hours. During the dialysis process, the distilled water is refreshed every 5-7 hours. After the dialysis is completed, the dialysate is dried in an oven at 60-70° C. for 10-15 hours to obtain the final sulfonated lignin product.

[0023] Furthermore, the step (4) of adding sodium hydroxide solution specifically comprises: adding sodium hydroxide solution with a concentration of 0.1 mol / L according to a material-liquid ratio of 1:40 (g:v).

[0024] The present invention has at least the following beneficial effects:

[0025] The invention discloses a method for utilizing multiple components of camellia oleifera shells. Through scientific technical process conditions, full utilization of camellia oleifera shells is achieved, and the problem of limited multi-component and high-value utilization of camellia oleifera shells is solved. At present, many public methods extract tea saponin components from camellia oleifera shells, and the residues after extraction are discarded, but in fact, camellia oleifera shells also contain rich high-value components. The present application obtains tea saponin, tannin, oligoxylose and lignin sulfonate from the camellia oleifera shells through a series of operations, fully utilizes the camellia oleifera shells, separates and purifies multiple chemical components, and prepares high-value-added chemical products, which is of great significance. [Specific implementation method]

[0026] In order to make the above-mentioned purpose, features and advantages of the present invention more obvious and easy to understand, the specific implementation of the present invention is described in detail below. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by the specific implementation disclosed below.

[0027] Embodiment 1:

[0028] This embodiment provides a method for utilizing multiple components of camellia oleifera shells, the method comprising the following steps:

[0029] (1) Pretreatment: Mix the camellia oleifera shell with water at a solid-liquid ratio of 1:25, and then extract under ultrasonic conditions at a temperature of 45° C. for 15 min to obtain an extract concentrate, dry the extract concentrate to obtain a crude extract for later use, and naturally air-dry the camellia oleifera residue obtained after the extraction to obtain a residue A for later use;

[0030] (2) Extracting tea saponin and tannin: adding water to the crude extract to make the resulting solution concentration 0.5 g / L, then adding n-butanol to the resulting solution at a volume ratio of 2:1 and stirring for 0.5 h, then standing to separate the liquids; concentrating and drying the supernatant to obtain tea saponin, and concentrating and drying the lower supernatant to obtain tannic acid;

[0031] (3) Extracting oligoxylose: adding 0.5% formic acid to residue A at a solid-liquid ratio of 1:9, and then reacting in a reactor at 160° C. for 15 minutes. After the reaction is completed, the reactor is placed in cold water to cool, and then the reactants in the reactor are filtered and separated with a polyamide filter to obtain an extract and a residue. The residue is rinsed with deionized water until neutral, the formic acid on the surface is removed, and air-dried to obtain residue B for standby use; the extract is concentrated under reduced pressure to 1 / 3 of the original volume, and then 3 times the volume of ethanol is added to the concentrate, stirred and mixed for 4 minutes, and allowed to stand for 3.5 hours until the oligoxylose is precipitated, the supernatant is absorbed by siphoning, and the ethanol is recovered by reduced pressure distillation. The precipitate is dried to obtain oligoxylose;

[0032] (4) Preparation of sodium lignin sulfonate: Residue B is placed in a reactor, and 0.1 mol / L NaOH solution is added according to a solid-liquid ratio of 1:40 (g:v), followed by adding 3-chloro-2-hydroxypropanesulfonic acid sodium salt accounting for 9% by mass of the residue B and stirring at a speed of 380 rpm for 1 hour. After the reaction, the reactor is immersed in cold water until the mixture therein cools to room temperature, and then the pH of the mixture is adjusted to 6.5 with a 20wt.% HCl solution. The mixture is transferred to a membrane dialysis bag with a molecular weight cutoff of 1000 g / mol and dialyzed in distilled water for 48 hours. During the dialysis process, the distilled water is refreshed every 5 hours. After the dialysis is completed, the dialyzate is dried in an oven at 60°C for 10 hours to obtain the final sulfonated lignin product.

[0033] Embodiment 2:

[0034] This embodiment provides a method for utilizing multiple components of camellia oleifera shells, the method comprising the following steps:

[0035] (1) Pretreatment: Mix the camellia oleifera shell with water at a solid-liquid ratio of 1:30, and then extract under ultrasonic conditions at a temperature of 50° C. for 20 min to obtain an extract concentrate, dry the extract concentrate to obtain a crude extract for later use, and naturally air-dry the camellia oleifera residue obtained after the extraction to obtain a residue A for later use;

[0036] (2) Extracting tea saponin and tannin: adding water to the crude extract to make the resulting solution concentration 1 g / L, then adding n-butanol to the resulting solution at a volume ratio of 2:1 and stirring for 1 h, then standing to separate the liquids; concentrating and drying the supernatant to obtain tea saponin, and concentrating and drying the lower supernatant to obtain tannic acid;

[0037] (3) Extracting xylo-oligosaccharides: adding 1% formic acid to residue A at a solid-liquid ratio of 1:10, and then reacting in a reactor at 160° C. for 20 minutes. After the reaction is completed, the reactor is placed in cold water to cool, and then the reactants in the reactor are filtered and separated with a polyamide filter to obtain an extract and a residue. The residue is rinsed with deionized water until it is neutral, the formic acid on the surface is removed, and air-dried to obtain residue B for later use; the extract is concentrated under reduced pressure to 1 / 3 of the original volume, and then ethanol 3 times the volume of the concentrate is added, stirred and mixed for 5 minutes, and allowed to stand for 4 hours until the xylo-oligosaccharides are precipitated, the supernatant is absorbed by siphoning, and the ethanol is recovered by reduced pressure distillation. The precipitate is dried to obtain xylo-oligosaccharides;

[0038] (4) Preparation of sodium lignin sulfonate: Residue B is placed in a reactor, and 0.1 mol / L NaOH solution is added according to a solid-liquid ratio of 1:40 (g:v), followed by adding sodium 3-chloro-2-hydroxypropanesulfonate accounting for 10% by mass of the residue B, and stirring at a speed of 400 rpm for 2 h. After the reaction, the reactor is immersed in cold water until the mixture therein cools to room temperature, and then the pH of the mixture is adjusted to 7.0 with a 20 wt.% HCl solution. The mixture is transferred to a membrane dialysis bag with a molecular weight cutoff of 1000 g / mol and dialyzed in distilled water for 48 hours. During the dialysis process, the distilled water is refreshed every 6 hours. After the dialysis is completed, the dialyzate is dried in an oven at 65°C for 12 hours to obtain the final sulfonated lignin product.

[0039] Embodiment 3:

[0040] This embodiment provides a method for utilizing multiple components of camellia oleifera shells, the method comprising the following steps:

[0041] (1) Pretreatment: The oil-tea camellia shells were mixed with water at a solid-liquid ratio of 1:35, and then extracted under ultrasonic conditions at a temperature of 55° C. for 25 min to obtain an extract concentrate, which was dried to obtain a crude extract for later use. Meanwhile, the oil-tea camellia fruit residue obtained after the extraction was naturally air-dried to obtain a residue A for later use;

[0042] (2) Extracting tea saponin and tannin: adding water to the crude extract to make the resulting solution concentration 1.5 g / L, then adding n-butanol to the resulting solution at a volume ratio of 2:1 and stirring for 1.5 h, then standing to separate the liquids; concentrating and drying the supernatant to obtain tea saponin, and concentrating and drying the lower supernatant to obtain tannic acid;

[0043] (3) Extracting xylo-oligosaccharides: adding 1.5% formic acid to residue A at a solid-liquid ratio of 1:12, and then reacting in a reactor at 160° C. for 25 minutes. After the reaction is completed, the reactor is placed in cold water to cool, and then the reactants in the reactor are filtered and separated with a polyamide filter to obtain an extract and a residue. The residue is rinsed with deionized water until neutral, the formic acid on the surface is removed, and air-dried to obtain residue B for standby use; the extract is concentrated under reduced pressure to 1 / 3 of the original volume, and then ethanol in an amount of 3 times the volume of the concentrate is added, stirred and mixed for 6 minutes, and allowed to stand for 4.5 hours until the xylo-oligosaccharides are precipitated, the supernatant is absorbed by siphoning, and the ethanol is recovered by reduced pressure distillation. The precipitate is dried to obtain xylo-oligosaccharides;

[0044] (4) Preparation of sodium lignin sulfonate: Residue B is placed in a reactor, and a sodium hydroxide solution with a concentration of 0.1 mol / L is added at a solid-liquid ratio of 1:40 (g:v). NaOH solution is added to the obtained solution, and then 3-chloro-2-hydroxypropanesulfonic acid sodium is added at a mass fraction of 12% of the mass of residue B, and stirred at a speed of 420 rpm for 3 hours. After the reaction, the reactor is immersed in cold water until the mixture therein cools to room temperature, and then the pH of the mixture is adjusted to 7.5 with a 20wt.% HCl solution. The mixture is transferred to a membrane dialysis bag with a molecular weight cutoff of 1000 g / mol and dialyzed in distilled water for 48 hours. During the dialysis process, the distilled water is refreshed every 7 hours. After the dialysis is completed, the dialyzate is dried in an oven at 70°C for 15 hours to obtain the final sulfonated lignin product.

[0045] Test example:

[0046] In order to illustrate the effect of this application, the applicant conducted the following tests:

[0047] Test 1: Testing tea saponins and tannins

[0048] This experiment tested the extraction rate of tea saponins and tannins obtained by each group of methods, and the groups were as follows:

[0049] The first group: tea saponin and tannin prepared in the manner of Example 2;

[0050] The second group: the oil tea fruit shells were mixed with water at a solid-liquid ratio of 1:30, and then leached for 20 minutes at a water bath temperature of 50°C to obtain an extract concentrate, which was dried to obtain a crude extract for later use, and the oil tea fruit residue obtained after the extraction was naturally air-dried to obtain residue A for later use; water was added to the crude extract to make the concentration of the obtained solution 1g / L, and then n-butanol was added to the obtained solution at a volume ratio of 2:1 and stirred for 1h, and then allowed to stand for separation; the supernatant was concentrated and dried to obtain tea saponin, and the supernatant was concentrated and dried to obtain tannic acid;

[0051] The third group: the oil tea fruit shell was mixed with 75% ethanol at a solid-liquid ratio of 1:10, and the mixture was extracted at a temperature of 50°C for 10 minutes, and then the extract was filtered to obtain the extract, and the extract concentrate was dried to obtain a crude extract for use, and the oil tea fruit residue obtained after the extraction was naturally air-dried to obtain residue A for use; water was added to the crude extract to make the concentration of the obtained solution 1g / L, and then n-butanol was added to the obtained solution at a volume ratio of 2:1 and stirred for 1h, and then the solution was allowed to stand for separation; the supernatant was concentrated and dried to obtain tea saponin, and the supernatant was concentrated and dried to obtain tannic acid;

[0052] The test results of the extraction rates of tea saponin and tannin in each group are shown in Table 1:

[0053] Table 1

[0054] Tea saponin extraction rate Tannin extraction rate Group 1 90.45％ 73.87％ Group 2 80.15％ 55.34％ Group 3 83.8％ 62.10％

[0055] According to the results in Table 1, the extraction rate of tea saponin and tannin obtained after treatment in the manner of the present application is relatively high. Since the cavitation effect of ultrasound in water destroys the structure of the plant cell wall to a certain extent, the dissolution of tea saponin and tannin is significantly promoted.

[0056] Experiment 2: Testing xylo-oligosaccharides

[0057] This experiment tested the extraction rate of xylo-oligosaccharides obtained by the extraction method of each group, and the groups were as follows:

[0058] Group 1: xylo-oligosaccharides extracted in the manner of Example 2;

[0059] Group 2: Hydrolyze camellia oleifera shells with malic acid to prepare xylo-oligosaccharides;

[0060] Group 3: Using camellia oleifera shell as raw material to prepare xylo-oligosaccharides using glutamic acid;

[0061] The test results are shown in Table 2:

[0062] Table 2

[0063] Xylooligosaccharide extraction rate Group 1 60.58％ Group 2 51.28％ Group 3 53.32％

[0064] According to the results in Table 2, the extraction method of the present application has a higher extraction rate of xylooligosaccharides, which may be because formic acid is a short-chain organic acid, which has a better mass transfer effect than malic acid and glutamic acid, and can better hydrolyze hemicellulose into monosaccharides or oligosaccharides.

[0065] Test 3: Testing Sodium Lignosulfonate

[0066] The present application further subjected the residues from the extraction of oligoxylose to a series of treatments to obtain sodium lignosulfonate. In order to test its performance, the applicant conducted the following experiments:

[0067] This test tests the degree of substitution and charge density of sodium lignin sulfonate extracted by each group of methods, and the groups are as follows:

[0068] Group 1: sodium lignin sulfonate extracted in the manner of Example 2;

[0069] Determination of charge density:

[0070] In this set of experiments, 0.2 g of sodium lignin sulfonate sample was dissolved in 20 mL of distilled water, and the solution was shaken in a water bath shaker at 30 °C and 150 rpm for 1 hour. The charge density of the prepared solution was measured using a particle charge detector, and the solution concentration was 0.005 mol / L.

[0071] The sulfonic acid groups attached to the sample were measured by water potentiometric titration using an automatic potentiometer. In this experiment, 1 g of sample was added to 100 mL of distilled water and the pH of the solution was adjusted to 7.0 with 1 mol / L HCl. The solution was then titrated with the cationic polymer TEGOtranta 100 to determine the number of sulfonic acid groups. The degree of substitution was calculated according to the following formula:

[0072] Degree of substitution = (M×A) / (1-0.117×A)

[0073] Wherein, A is the total sulfonic acid content (mmol / g), 0.117 (g / mmol) is the net mass increase of each sodium methylthioate connected to lignin, and M is the mass of the lignin basic unit (the mass of the C9 lignin unit is 0.188 g / mmol).

[0074] Group 2: Residue B was placed in a reactor, water was added thereto at a solid-liquid ratio of 1:10, and the mixture was stirred at a speed of 200 rpm for 10 min. At a constant temperature of 80°C, NaOH solution was added to the obtained solution to adjust the pH of the solution to 10, and then 3-chloro-2-hydroxypropanesulfonic acid sodium accounting for 10% of the mass fraction of residue B was added and stirred at a speed of 400 rpm for 4 h. After the reaction, the reactor was immersed in cold water until the mixture therein cooled to room temperature, and then the pH of the mixture was adjusted to 7.0 with a 20wt.% HCl solution. The mixture was transferred to a membrane dialysis bag with a molecular weight cutoff of 1000 g / mol and dialyzed in distilled water for 48 hours. During the dialysis process, the distilled water was refreshed every 6 hours. After the dialysis was completed, the dialyzate was dried in an oven at 65°C for 12 hours to obtain the final sulfonated lignin product. The charge density and degree of substitution were determined according to the method of the first group of experiments.

[0075] Group 3: Commercial sodium lignin sulfonate. The charge density and degree of substitution were determined as in Group 1.

[0076] The test results are shown in Table 3:

[0077] Table 3

[0078] Degree of substitution (mmol / g) Charge density (mequiv / g) Group 1 0.34 3.65 Group 2 0.12 1.18 Group 3 0.21 2.26

[0079] According to the results in Table 3, the sodium lignosulfonate prepared by the method of the present application has more excellent performance.

[0080] The descriptions of several embodiments of the present invention are relatively specific and detailed, but they should not be construed as limiting the scope of the present invention. It should be noted that, for those of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the attached claims.

Claims

1. A method for utilizing multiple components of camellia oleifera shells, characterized in that: The method comprises the following steps: (1) Pretreatment: Mixing the camellia oleifera shell with water, followed by extraction under ultrasonic conditions to obtain an extract concentrate, drying the extract concentrate to obtain a crude extract for later use, and naturally air-drying the camellia oleifera fruit residue obtained after the extraction to obtain a residue A for later use; (2) Extracting tea saponin and tannin: adding water to the crude extract, then adding n-butanol to the resulting solution and stirring for 0.5-1.5 hours, then standing to separate the liquids; concentrating and drying the supernatant to obtain tea saponin, and concentrating and drying the lower supernatant to obtain tannic acid; (3) Extracting xylo-oligosaccharides: adding 0.5-1.5% formic acid to the residue A, and then reacting in a reactor for 15-25 minutes. After the reaction is completed, the reactor is placed in water to cool, and then the reactants in the reactor are filtered and separated to obtain an extract and a residue. The residue is rinsed with deionized water until neutral, air-dried, and a residue B is obtained for later use; the extract is concentrated under reduced pressure, and then ethanol is added, stirred and mixed, and then allowed to stand until the xylo-oligosaccharides are precipitated, the supernatant is absorbed, and the ethanol is recovered by distillation under reduced pressure. The precipitate is dried to obtain xylo-oligosaccharides; (4) Preparation of sodium lignin sulfonate: Residue B is placed in a reactor, sodium hydroxide solution is added, and then sodium 3-chloro-2-hydroxypropanesulfonate is added and stirred for reaction. After the reaction, the reactor is immersed in water until the mixture therein cools to room temperature, and then the pH of the mixture is adjusted to 6.5-7.5 with HCl solution. The mixture is transferred to a membrane dialysis bag, dialyzed in distilled water, and the dialyzate is dried to obtain the final sulfonated lignin product.

2. The method according to claim 1, characterized in that In the step (1), the solid-liquid ratio of camellia oleifera shell to water is 1:25-35, the ultrasonic extraction temperature is 45-55° C., and the ultrasonic extraction time is 15-25 min.

3. The method according to claim 2, characterized in that In the step (1), the solid-liquid ratio of camellia oleifera shell to water is 1:30, the ultrasonic extraction temperature is 50° C., and the ultrasonic extraction time is 20 min.

4. The method according to claim 1, characterized in that: In the step (2), water is added to the crude extract so that the concentration of the resulting solution is 0.5-1.5 g / L.

5. The method according to claim 1, characterized in that The volume ratio of the solution to n-butanol in step (2) is 2:

1.

6. The method according to claim 1, characterized in that In the step (3), the material-liquid ratio of the residue A to formic acid is 1:9-12.

7. The method according to claim 1, characterized in that The extract in step (3) is specifically concentrated under reduced pressure to 1 / 3 of the original volume, and then ethanol in an amount three times the volume of the concentrate is added, stirred and mixed for 4-6 minutes, and allowed to stand for 3.5-4.5 hours to allow the xylooligosaccharide to precipitate.

8. The method according to claim 1, characterized in that: In the step (4), the amount of sodium 3-chloro-2-hydroxypropanesulfonate added is 9-12% of the mass of the residue B. The stirring reaction of sodium 3-chloro-2-hydroxypropanesulfonate is carried out at a speed of 380-420 rpm for 1-4 hours, and the reaction temperature is 100°C.

9. The method according to claim 1, characterized in that: In the step (4), the molecular weight cut-off of the membrane dialysis bag is 900-1100 g / mol, and the dialysis is carried out in distilled water for 48 hours. During the dialysis process, the distilled water is refreshed every 5-7 hours. After the dialysis is completed, the dialysate is vacuum dried in an oven at 60-70° C. for 10-15 hours to obtain the final sulfonated lignin product.

10. The method according to claim 1, characterized in that The step (4) of adding the sodium hydroxide solution specifically comprises: adding the sodium hydroxide solution having a concentration of 0.1 mol / L according to a material-liquid ratio of 1:40 (g:v).