A porous phosphoric acid-based polymer material, a preparation method thereof, and a method for extracting xylan from bagasse

Abstract

The application provides a phosphoric acid site polymer porous material and a preparation method thereof, and a method for extracting xylan from sugarcane residue. Compared with the traditional acid method for extracting xylan, the method for extracting xylan has high selectivity for extracting xylan due to the rich acid sites of the phosphoric acid site polymer porous material; meanwhile, the introduction of sodium ions can solubilize the fibers, help hydrogen ions to better penetrate into the fibers, and help to improve the xylan yield; the phosphoric acid site polymer porous material has similar properties to zeolite and has ion slow-release function, the hydrogen ions in the phosphoric acid site polymer can slowly release into the solution, which can reduce the acidity required for the xylan extraction reaction, and also reduces the equipment requirement for extracting xylan; the degradation liquid obtained after the xylan is extracted by the process has a low COD value, and the recycling utilization can be realized under the condition of stable extraction of xylan, and zero emission is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of xylan extraction, and particularly relates to a phosphoric acid-based polymer porous material, a preparation method thereof, and a method for extracting xylan from bagasse. BACKGROUND

[0002] A traditional acid method for extracting xylan is to contact and react dilute sulfuric acid (1-5% w / v) with fibers at 120 DEG C to 180 DEG C and a pressure of up to 1.01 MPa, and generally a high xylan yield (i.e. 9.2 g of xylan is produced from 100 g of bagasse) can be obtained, but the subsequent hydrolysis liquid has a too high acidity, toxic acid compounds are easily produced, are difficult to separate and recover, and a high corrosion resistance of equipment is required. In view of this, it is necessary to develop a xylan extraction process which overcomes the above-mentioned shortcomings.

[0003] Solid acid has been reported to be used for converting cellulose into glucose for sugar production, and at present, solid acid salt powder is mostly used in biomass, but hydrochloric acid or sulfamic acid is easily produced in the reaction, and the equipment is also corrosive.

[0004] Based on the defects of the current acid method for extracting xylan, it is necessary to improve it. SUMMARY

[0005] Therefore, the present application provides a phosphoric acid-based polymer porous material, a preparation method thereof, and a method for extracting xylan from bagasse, so as to solve the defects in the prior art.

[0006] In a first aspect, the present application provides a phosphoric acid-based polymer porous material, which comprises the following raw materials: phosphoric acid, metakaolin, water, sodium sulfate, hydrogen peroxide and sodium dodecyl sulfate.

[0007] Preferably, the mass ratio of the phosphoric acid, metakaolin, water, sodium sulfate, hydrogen peroxide and sodium dodecyl sulfate in the phosphoric acid-based polymer porous material is (500-800):(400-700):(80-130):(8-15):(6-12):(1-5).

[0008] In a second aspect, the present application further provides a preparation method of the phosphoric acid-based polymer porous material, which comprises the following steps:

[0009] After the phosphoric acid, metakaolin and water are stirred and mixed, the sodium sulfate, hydrogen peroxide and sodium dodecyl sulfate are added and continuously stirred and mixed to obtain a slurry;

[0010] After the slurry is cured, it is heated and solidified to obtain the phosphoric acid-based polymer porous material.

[0011] Preferably, in the preparation method of the phosphoric acid-based geopolymer porous material, the curing temperature in the curing step of the slurry is 60-100 DEG C, and the curing time is 5-10 days.

[0012] Preferably, in the preparation method of the phosphoric acid-based geopolymer porous material, the heating and curing temperature in the heating and curing step after the curing of the slurry is 230-270 DEG C, and the heating and curing time is 0.5-2 hours.

[0013] In a third aspect, the present application further provides a method for extracting xylan from bagasse, comprising the following steps:

[0014] After the bagasse fiber and the phosphoric acid-based geopolymer porous material are mixed, water is added, and after hydrothermal reaction, a hydrolysis liquor is collected, a precipitate is separated out, and drying is performed to obtain the xylan.

[0015] The phosphoric acid-based geopolymer porous material or the phosphoric acid-based geopolymer porous material prepared by the preparation method.

[0016] Preferably, in the method for extracting xylan from bagasse, the reaction temperature of the hydrothermal reaction is 120-160 DEG C, and the time is 2-5 hours.

[0017] Preferably, in the method for extracting xylan from bagasse, the mass ratio of the phosphoric acid-based geopolymer porous material to the bagasse fiber is 1:(1-5).

[0018] The mass ratio of the bagasse fiber to water is 1:(6-10).

[0019] Preferably, in the method for extracting xylan from bagasse, after the bagasse fiber and the phosphoric acid-based geopolymer porous material are mixed, water is added, and after hydrothermal reaction, solid-liquid separation is performed, a hydrolysis liquor is collected, the pH value is adjusted to 5-5.5, alcohol is added, and after standing, a precipitate is separated out and dried to obtain the xylan.

[0020] Preferably, in the method for extracting xylan from bagasse, NaOH is used to adjust the pH value to 5-5.5, and the alcohol is ethanol.

[0021] The present application has the following beneficial effects relative to the prior art:

[0022] 1. The phosphoric acid-based geopolymer porous material comprises phosphoric acid, metakaolin, sodium sulfate, hydrogen peroxide and sodium dodecyl sulfate; the strength of the phosphoric acid-activated geopolymer is higher than that of the alkali-activated geopolymer, and the acid resistance is good; and the slow-release hydrogen ion effect of the phosphoric acid-based geopolymer porous material itself maintains the pH value of the reaction environment, and the active sites can be used to degrade hemicellulose to obtain xylan.

[0023] 2. The method for extracting xylan from sugarcane bagasse of the present invention, compared with the traditional acid extraction method, exhibits high selectivity for xylan extraction due to the abundant acidic sites of the phosphate-based polymer porous material. Simultaneously, the introduction of sodium ions can solubilize the fiber, helping hydrogen ions to better penetrate into the fiber, thus improving the xylan yield. The phosphate-based polymer porous material of the present invention has properties similar to zeolite, thus possessing ion-releasing function. Hydrogen ions in the phosphate-based polymer can be slowly released into the solution, reducing the acidity required for the xylose extraction reaction and lowering the equipment requirements for xylan extraction. The degradation liquid obtained after xylan extraction by this process has a low COD value and can be recycled while maintaining stable xylan extraction, achieving zero emissions. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a SEM image of the phosphate-based polymer porous material prepared in Example 1 of the present invention;

[0026] Figure 2 This is a graph showing the pH change over time during the xylan extraction process according to the method of the present invention.

[0027] Figure 3 The graph shows the effect of the number of cycles on the xylan extraction rate.

[0028] Figure 4 The effect of the number of cycles on the COD value. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0030] It is to be noted that the order of description of the following embodiments is not intended to imply a preference of such order. Additionally, in the description of the present application, the term "including" means "including but not limited to". Various embodiments of the present application can exist in a range of forms; it should be understood that the description in a range form is merely for the convenience and brevity, and should not be understood as a rigid limitation on the scope of the present application; therefore, it should be considered that the range description has been specifically disclosed all possible sub-ranges and single values in the range. For example, it should be considered that the range description from 1 to 6 has been specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single values in the range, such as 1, 2, 3, 4, 5 and 6, regardless of the range. In addition, whenever a numerical range is indicated in this document, it refers to any cited number (fraction or integer) in the indicated range.

[0031] The embodiment of the present application provides a phosphoric acid-based geopolymer porous material, which comprises the following raw materials: phosphoric acid, metakaolin, water, sodium sulfate, hydrogen peroxide and sodium dodecyl sulfate.

[0032] In some embodiments, the mass ratio of the phosphoric acid, metakaolin, water, sodium sulfate, hydrogen peroxide and sodium dodecyl sulfate is (500-800):(400-700):(80-130):(8-15):(6-12):(1-5).

[0033] Based on the same inventive concept, the present application also provides a preparation method of the above-mentioned phosphoric acid-based geopolymer porous material, comprising the following steps:

[0034] S1, after stirring and mixing the phosphoric acid, metakaolin and water, adding sodium sulfate, hydrogen peroxide and sodium dodecyl sulfate to continue stirring and mixing to obtain a slurry;

[0035] S2, after curing the slurry, heating and curing to obtain the phosphoric acid-based geopolymer porous material.

[0036] The geopolymer is a new type of aluminosilicate inorganic polymer material with a three-dimensional network structure from amorphous to semi-crystalline state, which has similar properties to zeolites and can be considered to have similar effects to solid acid. The phosphoric acid-based geopolymer porous material has higher strength and better acid resistance than the alkali-based geopolymer activated by phosphoric acid; and the phosphoric acid-based geopolymer porous material itself has a slow-release hydrogen ion effect to maintain the pH value of the reaction environment, and can utilize the active site to degrade xylan in hemicellulose.

[0037] In some embodiments, in the step of curing the slurry, the curing temperature is 60-100 DEG C, and the curing time is 5-10 days.

[0038] In some embodiments, after the slurry is cured, the heating and curing step is performed at a temperature of 230-270 DEG C for 0.5-2 hours.

[0039] In some embodiments, the method for preparing the phosphoric acid-based polymer porous material comprises the following steps:

[0040] S1, after mixing phosphoric acid, metakaolin and water, adding sodium sulfate, hydrogen peroxide and sodium dodecyl sulfate and continuing to mix and stir to obtain a slurry;

[0041] S2, injecting the slurry in S1 into a mold, then placing it in a muffle furnace for curing at a temperature of 60-100 DEG C for 5-10 days, after demolding, placing the sample in a muffle furnace for heating and curing at a temperature of 230-270 DEG C for 0.5-2 hours to obtain a phosphoric acid-based polymer porous material.

[0042] Based on the same inventive concept, the present application also provides a method for extracting xylan from bagasse, comprising the following steps:

[0043] After mixing the bagasse fibers and the phosphoric acid-based polymer porous material, adding water, and after hydrothermal reaction, collecting the hydrolyzate, precipitating the precipitate, and drying, xylan is obtained.

[0044] In some embodiments, the reaction temperature of the hydrothermal reaction is 120-160 DEG C, and the reaction time is 2-5 hours.

[0045] In some embodiments, the mass ratio of the phosphoric acid-based polymer porous material to the bagasse fibers is 1:(1-5).

[0046] In some embodiments, the mass ratio of the phosphoric acid-based polymer porous material to the bagasse fibers is 1:(1-5).

[0047] The mass ratio of the bagasse fibers to water is 1:(6-10).

[0048] In some embodiments, after mixing the bagasse fibers and the phosphoric acid-based polymer porous material, adding water, and after hydrothermal reaction, solid-liquid separation is performed, the hydrolyzate is collected, the pH is adjusted to 5-5.5, alcohol is added, and after standing, the precipitate is precipitated and dried to obtain xylan.

[0049] In some embodiments, NaOH is used to adjust the pH to 5-5.5, and the alcohol is ethanol.

[0050] In some embodiments, after mixing the bagasse fiber and the phosphoric acid-based polymer porous material, water is added, and after hydrothermal reaction, solid-liquid separation is performed, and a hydrolysis liquor is collected, the pH of the hydrolysis liquor is adjusted to 5-5.5 using NaOH, 2 times the volume (i.e. 2 times the volume of the hydrolysis liquor) of 95% volume concentration ethanol is added, and after standing for 30 min, the precipitate is separated out and dried to obtain xylan.

[0051] In some embodiments, the bagasse fiber is prepared by the following method: the bagasse is cut and bagasse fibers of 40-80 mesh are selected, and the selected bagasse fibers are dried in an oven at 100 DEG C for 24 h.

[0052] Compared with the traditional acid method for extracting xylan, the method for extracting xylan according to the present application has high selectivity for extracting xylan due to the rich acid sites of the phosphoric acid-based polymer porous material; meanwhile, the introduction of sodium ions can solubilize the fibers, help hydrogen ions to better penetrate into the fibers, and help to improve the yield of xylan; the phosphoric acid-based polymer porous material has similar properties to zeolite and thus has ion slow-release function, the hydrogen ions in the phosphoric acid-based polymer can be slowly released into the solution, which can reduce the acidity required for the xylan extraction reaction and also reduce the equipment requirements for extracting xylan; the degradation liquor obtained after the process for extracting xylan has a low COD value, and the recycling and zero discharge can be realized under the condition of stable extraction of xylan.

[0053] The following further illustrates the phosphoric acid-based polymer porous material and the preparation method thereof and the method for extracting xylan according to the present application with specific embodiments. This part further illustrates the content of the present application in combination with specific embodiments, but should not be understood as a limitation on the present application. Unless otherwise specified, the technical means adopted in the embodiments are conventional means familiar to those skilled in the art. Unless otherwise specified, the reagents, methods and equipment adopted in the present application are conventional reagents, methods and equipment in the art.

[0054] In the following embodiments, the bagasse fiber is prepared by the following method: the bagasse is cut and bagasse fibers of 60 mesh are selected, and the selected bagasse fibers are dried in an oven at 100 DEG C for 24 h to obtain the bagasse fiber.

[0055] Embodiment 1

[0056] The embodiment of the present application provides a phosphoric acid-based polymer porous material, which comprises the following raw materials in parts by weight: 650 parts of phosphoric acid, 500 parts of metakaolin, 100 parts of water, 12 parts of sodium sulfate, 10 parts of hydrogen peroxide and 1 part of sodium dodecyl sulfate.

[0057] The preparation method of the above-mentioned phosphoric acid-based polymer porous material comprises the following steps:

[0058] S1, the phosphoric acid, metakaolin and water are stirred and mixed, then sodium sulfate, hydrogen peroxide and sodium dodecyl sulfate are added and continuously stirred and mixed to obtain a slurry;

[0059] S2, the slurry in S1 is injected into a mold, then placed in a muffle furnace at a temperature of 80 DEG C for 7 days, after demolding, the sample is placed in a muffle furnace at 250 DEG C for 1 hour of heating and curing, to obtain a phosphoric acid-based polymer porous material.

[0060] The embodiment of the application further provides a method for extracting xylan from bagasse, comprising the following steps:

[0061] The bagasse fiber and the phosphoric acid-based polymer porous material prepared in the embodiment 1 are mixed, then placed in a reactor, water is added, and heated at 150 DEG C for 4 hours of reaction; after the reaction is completed, the solid-liquid separation is carried out by using filter cloth to obtain a hydrolysis liquor, the pH of the hydrolysis liquor is adjusted to 5 by using NaOH, then 2 times of 95% (volume concentration) ethanol is added, and the mixture is left to stand for 30 minutes, so that the precipitate is separated out, and dried to obtain xylan.

[0062] The mass ratio of the phosphoric acid-based polymer porous material to the bagasse fiber is 1:3, and the mass ratio of the bagasse fiber to water is 1:8.

[0063] Embodiment 2

[0064] The embodiment of the application provides a phosphoric acid-based polymer porous material, which comprises the following raw materials in parts by weight: 500 parts of phosphoric acid, 400 parts of metakaolin, 80 parts of water, 13 parts of sodium sulfate, 6 parts of hydrogen peroxide and 3.5 parts of sodium dodecyl sulfate.

[0065] The preparation method of the above-mentioned phosphoric acid-based polymer porous material comprises the following steps:

[0066] S1, the phosphoric acid, metakaolin and water are stirred and mixed, then sodium sulfate, hydrogen peroxide and sodium dodecyl sulfate are added and continuously stirred and mixed to obtain a slurry;

[0067] S2, the slurry in S1 is injected into a mold, then placed in a muffle furnace at a temperature of 60 DEG C for 7 days, after demolding, the sample is placed in a muffle furnace at 250 DEG C for 1 hour of heating and curing, to obtain a phosphoric acid-based polymer porous material.

[0068] The embodiment of the application further provides a method for extracting xylan from bagasse, comprising the following steps:

[0069] The bagasse fiber and the phosphoric acid-based polymer porous material prepared in Example 2 are mixed, then placed in a reactor, water is added, and heated at 160 DEG C for 3h; after the reaction is completed, the hydrolysis liquid is obtained by solid-liquid separation with filter cloth, the hydrolysis liquid is adjusted to pH = 5 with NaOH, then 2 times the volume of 95% (volume concentration) ethanol is added, and left to stand for 30 min, so that the precipitate is separated out, dried to obtain xylan;

[0070] The mass ratio of the phosphoric acid-based polymer porous material to the bagasse fiber is 1:4, and the mass ratio of the bagasse fiber to water is 1:6.

[0071] Example 3

[0072] The example of the present application provides a kind of phosphoric acid-based polymer porous material, including the following weight parts raw materials: 800 parts of phosphoric acid, 750 parts of metakaolin, 130 parts of water, 15 parts of sodium sulfate, 8 parts of hydrogen peroxide, 5 parts of sodium dodecyl sulfate.

[0073] The preparation method of the above-mentioned phosphoric acid-based polymer porous material includes the following steps:

[0074] S1, after stirring and mixing phosphoric acid, metakaolin and water, continue to stir and mix sodium sulfate, hydrogen peroxide and sodium dodecyl sulfate to obtain slurry;

[0075] S2, the slurry in S1 is injected into a mold, then placed in a muffle furnace at a temperature of 100 DEG C for 7d, after demolding, the sample is placed in a muffle furnace at 250 DEG C, and heated and cured for 1h to obtain a phosphoric acid-based polymer porous material.

[0076] The example of the present application also provides a method for extracting xylan from bagasse, including the following steps:

[0077] The bagasse fiber and the phosphoric acid-based polymer porous material prepared in Example 3 are mixed, then placed in a reactor, water is added, and heated at 150 DEG C for 2.5h; after the reaction is completed, the hydrolysis liquid is obtained by solid-liquid separation with filter cloth, the hydrolysis liquid is adjusted to pH = 5 with NaOH, then 2 times the volume of 95% (volume concentration) ethanol is added, and left to stand for 30 min, so that the precipitate is separated out, dried to obtain xylan;

[0078] The mass ratio of the phosphoric acid-based polymer porous material to the bagasse fiber is 1:5, and the mass ratio of the bagasse fiber to water is 1:9.

[0079] Example 4

[0080] The example of the present application provides a kind of phosphoric acid-based polymer porous material, including the following weight parts raw materials: 750 parts of phosphoric acid, 700 parts of metakaolin, 120 parts of water, 8 parts of sodium sulfate, 12 parts of hydrogen peroxide, 4 parts of sodium dodecyl sulfate.

[0081] The preparation method of the phosphoric acid-based polymer porous material comprises the following steps:

[0082] S1, after stirring and mixing phosphoric acid, metakaolin and water, adding sodium sulfate, hydrogen peroxide and sodium dodecyl sulfate to continue stirring and mixing to obtain a slurry;

[0083] S2, the slurry in S1 is injected into a mold, and then placed in a muffle furnace at a temperature of 90°C for 7d, after demolding, the sample is placed in a muffle furnace at 250°C for heating and curing for 1h, to obtain a phosphoric acid-based polymer porous material.

[0084] The application also provides a method for extracting xylan from bagasse, comprising the following steps:

[0085] The bagasse fibers and the phosphoric acid-based polymer porous material prepared in Example 4 are mixed and placed in a reactor, water is added, and heated at 120°C for 2.5h; after the reaction is completed, the solid-liquid separation is carried out with filter cloth to obtain a hydrolysis liquid, the pH of the hydrolysis liquid is adjusted to 5 with NaOH, then 2 times the volume of 95% (volume concentration) ethanol is added, and the mixture is allowed to stand for 30min, so that the precipitate is separated out, and dried to obtain xylan;

[0086] The mass ratio of the phosphoric acid-based polymer porous material to the bagasse fibers is 1:1, and the mass ratio of the bagasse fibers to water is 1:10.

[0087] Comparative Example 1

[0088] This comparative example is designed to illustrate that the introduction of sodium ions helps to extract xylan, with Example 1 as a reference.

[0089] Specifically, Comparative Example 1 provides a phosphoric acid-based polymer porous material, which comprises the following raw materials by weight: 650 parts of phosphoric acid, 500 parts of metakaolin, 100 parts of water, 10 parts of hydrogen peroxide and 1 part of sodium dodecyl sulfate.

[0090] The preparation method of the phosphoric acid-based polymer porous material comprises the following steps:

[0091] S1, after stirring and mixing phosphoric acid, metakaolin and water, adding hydrogen peroxide and sodium dodecyl sulfate to continue stirring and mixing to obtain a slurry;

[0092] S2, the slurry in S1 is injected into a mold, and then placed in a muffle furnace at a temperature of 80°C for 7d, after demolding, the sample is placed in a muffle furnace at 250°C for heating and curing for 1h, to obtain a phosphoric acid-based polymer porous material.

[0093] The application also provides a method for extracting xylan from bagasse, comprising the following steps:

[0094] The bagasse fiber and the phosphoric acid-based polymer porous material prepared in Comparative Example 1 were mixed and placed in a reactor, water was added, and the mixture was heated at 150°C for 4h; after the reaction was completed, the hydrolysis liquid was obtained by solid-liquid separation with filter cloth, the pH of the hydrolysis liquid was adjusted to 5 with NaOH, 2 times volume of 95% (volume concentration) ethanol was added, and the mixture was allowed to stand for 30 min, so that the precipitate was separated out, and the precipitate was dried to obtain xylan;

[0095] The mass ratio of the phosphoric acid-based polymer porous material to the bagasse fiber was 1:3, and the mass ratio of the bagasse fiber to water was 1:8.

[0096] Comparative Example 2

[0097] In order to highlight the advantages of the process for extracting xylan, a method for extracting xylan by traditional acid method was provided as Comparative Example 2.

[0098] The present comparative example provided a method for extracting xylan from bagasse, comprising the following steps:

[0099] The bagasse fiber and water were mixed and placed in a reactor, and sulfuric acid was added to adjust the pH value to 2, and the mixture was heated at 150°C for 4h; after the reaction was completed, the hydrolysis liquid was obtained by solid-liquid separation with filter cloth, the pH of the hydrolysis liquid was adjusted to 5 with NaOH, 2 times volume of 95% (volume concentration) ethanol was added, and the mixture was allowed to stand for 30 min, so that the precipitate was separated out, and the precipitate was dried to obtain xylan;

[0100] The mass ratio of the bagasse fiber to water was 1:8.

[0101] Performance test

[0102] 1. SEM test

[0103] The microstructure of the phosphoric acid-based polymer porous material prepared in Example 1 was tested, and the results are shown in Figure 1 .

[0104] As can be seen from Figure 1 , the phosphoric acid-based polymer material used in the process is a porous material with a large specific surface area.

[0105] 2. Xylan extraction rate determination

[0106] Within a certain range, the content of D-xylose is proportional to the absorbance of the solution, and the content of D-xylose in the sample can be determined by spectrophotometry, and the content of xylan is obtained by multiplying the obtained results by 0.88. The xylan extraction rates in Examples 1-4 and Comparative Examples 1-2 were tested according to the above method, and the results are shown in Table 1 below.

[0107] Table 1 - Xylan extraction rates of different examples and comparative examples

[0108] Comparative Example 1 Comparative Example 2 Example 1 Example 2 Example 3 Example 4 Xylan extraction rate (%) 6.5 2.7 7.5 6.3 5.1 5.4

[0109] As shown in Table 1, the xylan extraction rates of the methods in Examples 1-4 are all superior to the traditional acid method in Comparative Example 2, indicating that the extraction efficiency of xylan from phosphate-based porous polymer materials is higher than that of the traditional acid method. Furthermore, the xylan extraction rate of 7.5% in Example 1 is higher than the 6.5% in Comparative Example 1, suggesting that the introduction of sodium ions improves the xylan extraction efficiency.

[0110] 3. Selectivity test for xylan extraction

[0111] The changes in the mass percentages of cellulose, lignin, and hemicellulose in bagasse fiber before and after xylan extraction from the phosphate-based polymer porous material in Example 1 were determined using the paradigm method. The results are shown in Table 2.

[0112] Table 2 - Mass percentages of cellulose, lignin, and hemicellulose in sugarcane bagasse fiber before and after xylan extraction.

[0113] Before extraction of xylan After extraction of xylan Cellulose (%) 50.6 49.2 Lignin (%) 18.9 21.5 Hemicellulose (%) 29.3 10.8

[0114] Table 2 shows that the cellulose content did not change significantly before and after the reaction. The significant decrease in the mass percentage of hemicellulose indicates that most of the hemicellulose was hydrolyzed to form xylan; the increase in the mass percentage of lignin is because the mass percentage of hemicellulose decreased more significantly than that of lignin, thus increasing the mass percentage. These data demonstrate that this process has high selectivity for xylan extraction.

[0115] 4. Hydrogen ion sustained release test

[0116] Following the method described in Example 1, the pH change over time (1–15 h) during the reaction was measured using a pH meter to illustrate the hydrogen ion release effect of the phosphate-based polymer porous material in this process. The results are as follows: Figure 2 As shown.

[0117] Depend on Figure 2 As the reaction proceeds, the pH value of the reaction system decreases slowly, indicating that the porous material continuously releases hydrogen ions to meet the acidity required for the reaction. Specifically, the phosphate-based polymer porous material of the present invention has a slow-release effect on hydrogen ions. Although hydrogen ions are continuously consumed, the pH value of the reaction system can still be maintained between 2 and 3 within 4 hours.

[0118] 5. Regeneration and waste liquid recycling test of phosphate-based polymer porous materials

[0119] The reacted phosphoric acid-based polymer porous material in Example 1 was soaked in a phosphoric acid solution with pH = 2 for 1 h to restore the acid of the phosphoric acid-based polymer porous material. Meanwhile, the hydrolysis liquor in Example 1 was collected after separation of xylan, water was added to make up the lost water volume, and the regenerated porous material and the acid waste liquor were directly used for the next round of xylan extraction experiment. The experiment was cycled 6 times, and the COD value and xylan extraction rate of the hydrolysis liquor were measured each time. The results are shown in Figures 3-4 . Figure 3 The vertical coordinate is the xylan extraction rate, and the horizontal coordinate is the cycle number. Figure 4 The vertical coordinate is the COD value, and the horizontal coordinate is the cycle number.

[0120] As can be seen from Figure 3 , the xylan extraction rate in the hydrolysis liquor slightly decreased after six cycles of the phosphoric acid-based polymer porous material, but the xylan extraction rate remained at a relatively high level.

[0121] As can be seen from Figure 4 , the COD in the black liquor (i.e. the acid waste liquor after xylan extraction) was stable after five cycles. This is conducive to the subsequent treatment of the black liquor. The above data shows that the present process has the environmental protection and sustainability of not discharging waste water.

[0122] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method of extracting xylan from sugar cane bagasse, characterised in that, The method comprises the following steps: The bagasse fiber and the phosphoric acid-based polymer porous material are mixed, water is added, and a hydrolysis liquid is collected after a hydrothermal reaction. The phosphoric acid-based polymer porous material comprises the following raw materials: phosphoric acid, metakaolin, water, sodium sulfate, hydrogen peroxide, and sodium dodecyl sulfate. The mass ratio of the phosphoric acid, metakaolin, water, sodium sulfate, hydrogen peroxide, and sodium dodecyl sulfate is (500-800):(400-700):(80-130):(8-15):(6-12):(1-5).

2. The process for extraction of xylan from sugar cane bagasse as claimed in claim 1 wherein, The reaction temperature of the hydrothermal reaction is 120-160 DEG C, and the reaction time is 2-5 h.

3. The process for extraction of xylan from sugar cane bagasse as claimed in claim 1 wherein, The mass ratio of the phosphoric acid-based polymer porous material to the bagasse fiber is 1:(1-5). The mass ratio of the bagasse fiber to water is 1:(6-10).

4. The process for extraction of xylan from sugar cane bagasse as claimed in claim 1 wherein, The bagasse fiber and the phosphoric acid-based polymer porous material are mixed, water is added, and a hydrolysis liquid is collected after a hydrothermal reaction.

5. The method of extracting xylan from sugar cane bagasse as claimed in claim 4, wherein, The pH is adjusted to 5-5.5 using NaOH, and the alcohol is ethanol.

6. The process for extraction of xylan from sugar cane bagasse as claimed in claim 1 wherein, The preparation method of the phosphoric acid-based polymer porous material comprises the following steps: The phosphoric acid, metakaolin, and water are stirred and mixed, and then the sodium sulfate, hydrogen peroxide, and sodium dodecyl sulfate are added and stirred and mixed to obtain a slurry. The slurry is cured after maintenance, and the phosphoric acid-based polymer porous material is obtained.

7. The process for extraction of xylan from sugar cane bagasse as claimed in claim 6 wherein, In the step of maintaining the slurry, the maintenance temperature is 60-100 DEG C, and the maintenance time is 5-10 d.

8. The process for extraction of xylan from sugar cane bagasse as claimed in claim 6 wherein, In the step of curing the slurry after maintenance, the curing temperature is 230-270 DEG C, and the curing time is 0.5-2 h.

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