Method for extracting high-purity xylose liquid and cellulose using corn stover

Abstract

The present invention relates to a method for extracting high purity xylose liquid and cellulose from corn stover, which includes the steps of raw material selection, raw material pretreatment, alkali treatment, acid hydrolysis and stepwise alkali treatment. The present invention is to extract high purity xylose liquid and cellulose from corn stover by gradient selective purification, which maximizes the extraction of xylose from corn stover with the lowest possible cost process, while separating and extracting high purity cellulose products from stover residue.

Description

[Technical field]

[0001] The present invention belongs to the technical field of cellulose production, and in particular relates to a method for extracting high-purity xylose liquid and cellulose using corn stover. [Background technology]

[0002] Lignocellulosic feedstocks can be obtained from various sources, including agricultural residues, forest crops, industrial residues, etc. Corn stover is a type of agricultural residue that has the characteristics of being abundant, cheap, safe and renewable, and can be used as an alternative to fossil energy. The three main components in stover biomass feedstocks, namely cellulose, hemicellulose, and lignin, can be converted into various forms of high-value chemicals, which can reduce environmental problems and promote economic and social development. However, the various components in corn stover are closely connected, and it is difficult to separate and purify them for further value, so at present, most of the stover biomass is directly incinerated or discarded. In order to effectively improve the utilization rate of raw materials, it is very urgent to design a suitable processing method.

[0003] At present, the separation of the three components of stover mainly involves directly treating agricultural waste with acid solution or xylanase, hydrolyzing or enzymatically hydrolyzing the hemicellulose components to obtain xylose, then treating the residue with cellulase to obtain a glucose solution through enzymatic hydrolysis of cellulose, and finally fermenting the resulting glucose solution to produce ethanol. However, there are still many technical challenges that have yet to be resolved.

[0004] Issue 1: When corn stover is subjected to acid hydrolysis to obtain a hydrolysate, the composition of the hydrolysate is relatively complex and the purity of xylose is low, which affects the subsequent purification of xylose.

[0005] Challenge 2: When corn stover is enzymatically hydrolyzed with xylanase and cellulase to produce xylose and glucose, the cost of the enzymes is high, and the lignin components in corn stover adsorb the enzyme proteins during the enzymatic hydrolysis process, hindering the enzymatic hydrolysis process.

[0006] Challenge 3: Waste residues obtained by acid hydrolysis have low cellulose content and are of low value.

[0007] The cellulose content in agricultural waste residues containing cellulose currently used for enzymatic hydrolysis and fermentation is not very high. For example, in Patent Publication No. CN101696427A, corn cob raw material is pretreated with alkaline liquid, and then treated with hemicellulase to convert more than 45% of the hemicellulose into a xylose solution, while obtaining a cellulose residue with a cellulose content of only 76.03%. The cellulose residue is fermented with commercially available cellulase and alcohol-activated dry yeast to produce fuel ethanol, but the amount of ethanol obtained per gram of cellulose is only 0.522g, resulting in high production costs. For example, in Patent Publication No. CN103045677A, corn cobs are used as raw materials, which are first pretreated with alkali, then the alkali pretreatment residue is subjected to acid hydrolysis to extract pentose, and finally the acid hydrolysis residue is enzymatically hydrolyzed to produce a glucose solution, which is fermented to produce ethanol. The cellulose content of the acid hydrolysis residue used in this patent is even lower than that of the cellulose residue used in Patent CN101696427A, i.e., the cellulose content is not more than 76.03%. Summary of the Invention [Problem to be solved by the invention]

[0008] The technical problem that the present invention aims to solve is to provide a method for extracting high purity xylose liquid and cellulose from corn stover by gradient selective purification, which maximizes the extraction of high purity xylose from corn stover while separating and extracting high purity cellulose products from the stover residue under the lowest possible cost processing conditions. [Means for solving the problem]

[0009] The present invention is accomplished as follows.

[0010] Raw material selection: Step 1: Select and use corn stover raw material with a moisture content of 7% to 13%; Raw material pretreatment: First, the corn stover is crushed into powder with a particle size of 60 mesh to 300 mesh by a grinder, and then placed in a blower drying box and dried at 45°C for 22h to 26h to obtain absolutely dry powdered corn stover; Alkaline treatment: the absolute dry powdered corn stover obtained in step 2 is mixed with process water, and then the NaOH concentration in the system is adjusted to 0.1%-0.4% with a 30% concentrated alkaline solution, and the alkaline treatment is carried out at a temperature of 85°C-125°C for 1.2h-2.0h, and then centrifuged to obtain a stover residue and a centrifugal supernatant, and the stover residue is supplied to a xylose extraction process; Acid hydrolysis: The stem and leaf residue obtained in step 3 is mixed with 1.0% to 2.5% diluted H2SO4 in a predetermined ratio, and acid-hydrolyzed at 100°C to 160°C for 30 to 120 minutes. Then, the mixture is centrifuged to obtain an acid hydrolyzed liquid and an acid hydrolyzed stem and leaf residue. The acid hydrolyzed liquid is converted into a high-purity xylose liquid, and the acid hydrolyzed stem and leaf residue is subjected to a cellulose extraction process. Step 4. and (5) stepwise alkali treatment: mixing the acid hydrolyzed corn stover residue obtained in step 4 with process water, adjusting the NaOH concentration in the system with a 30% concentrated alkali solution to an initial concentration of 0.2%-1%, an initial temperature of 60°C-90°C, and then increasing the alkali concentration by 0.1%-0.5% every hour and increasing the temperature by 10°C-20°C for 4.0h-7.0h under the temperature for pretreatment, centrifuging the treated material, and washing the solid portion with water to obtain a product with a high cellulose content. Effect of the Invention

[0011] Compared with the prior art, the method for extracting high-purity xylose liquid and cellulose using corn stover of the present invention has a simple process, reduces costs, and has the following features:

[0012] 1. Corn stover is pretreated with 0.1-0.4% dilute alkali to remove impurities such as easily hydrolyzed lignin and colloids in plant cell walls while retaining most of the xylose unit components in the hemicellulose of the corn stover.

[0013] 2. The corn stover after dilute alkali treatment is subjected to dilute acid hydrolysis to hydrolyze the hemicellulose in the corn stover to convert it to xylose (conversion rate 77.4%), and a clear hydrolyzate liquid is obtained with few impurities and from which xylose can be easily separated. Both dilute alkali treatment and dilute acid treatment are carried out only once, and multi-stage treatment is not required, so the process is simplified, and the concentration of the dilute alkali used is only 0.1% (mass percent), and the concentration of the dilute sulfuric acid is 2.49% (mass percent).

[0014] 3. The acid hydrolyzed stalk residue (cellulose content 63.39%, hemicellulose content 0%, lignin etc. 36.61%) is further treated with alkali, and the alkali concentration and temperature (alkali) are gradually increased to remove components such as lignin in the acid hydrolyzed stalk residue, increase the cellulose content in the stalk residue, and finally treat with alkali to obtain a high-purity cellulose product with a cellulose content of 97.96%. A relatively pure cellulose product can be obtained by gradually increasing the alkali concentration and pretreatment temperature. The method of the present invention solves the following problems:

[0015] 1. Currently, the residue after extracting xylose from industrial waste is still directly burned as fuel, which means that the abundant cellulose components are not effectively extracted and utilized, resulting in a waste of resources.

[0016] 2. The xylose hydrolyzate obtained by acid hydrolysis of corn stover to extract xylose does not have a high purity and contains too many impurities, making it difficult to extract the xylose product through subsequent purification.

[0017] 3. Currently, the residue after xylose extraction from industrial waste contains lignin and other components, and the cellulose content is not very high, less than 76.03%. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] In order to clarify the technical problems, technical solutions and advantageous effects of the present invention, the present invention will be described in more detail below with reference to examples. It should be understood that the specific examples described herein are only used to illustrate the present invention and are not intended to limit the present invention.

[0019] A preferred embodiment of the method for extracting high purity xylose liquid and cellulose using corn stover of the present invention includes the following steps.

[0020] Step 1 Raw material selection: Select and use corn stover raw materials with a moisture content of 7%-13%.

[0021] Step 2 Raw material pretreatment: First, the corn stover is ground into powder with a particle size of 60 mesh to 300 mesh using a grinder, and then placed in a ventilation drying box and dried at 45°C for 22 to 26 hours to obtain absolutely dry powdered corn stover.

[0022] Step 3 Alkaline treatment: The absolute dry powdered corn stover obtained in step 2 is mixed with process water in a predetermined ratio, and then the NaOH concentration in the system is adjusted to 0.1%-0.4% with 30% concentrated alkaline solution, and alkaline treatment is carried out at a temperature of 85°C-125°C for 1.2h-2.0h, and then centrifuged to obtain stover residue and centrifugal liquid, and the stover residue is fed to the xylose extraction process. When 100g of corn stover is processed, 80.75g of residual solid is obtained, with the loss rate of xylose being less than 5% and the loss rate of cellulose being less than 4%.

[0023] Step 4 Acid hydrolysis: The stem and leaf residue obtained in step 3 is mixed with 1.0% to 2.5% diluted H2SO4 in a predetermined ratio and acid-hydrolyzed at 100°C to 160°C for 30 to 120 minutes, then centrifuged to obtain an acid hydrolysis liquid and an acid hydrolyzed stem and leaf residue. The acid hydrolysis liquid is subjected to a xylose extraction process to produce xylose. The acid hydrolysis liquid is made into a high-purity xylose liquid, and the acid hydrolyzed stem and leaf residue is subjected to a cellulose extraction process. After subjecting 100 g of raw stems and leaves to steps 2, 3, and 4, 53.11 g of acid hydrolyzed stem and leaf residue and 1.53 L of xylose hydrolysis liquid are obtained. The acid hydrolyzed stem and leaf residue contains 34.32 g of cellulose and 18.79 g of lignin, etc., and the xylose in the xylose hydrolysis liquid has a concentration of 11.84 g / L and a purity of 74.14%.

[0024] Step 5 Stepwise alkaline treatment: After mixing the acid hydrolyzed corn stover residue obtained in step 4 with process water in a predetermined ratio, adjust the NaOH concentration in the system with 30% concentrated alkaline solution, set the initial concentration to 0.2%-1%, and the initial temperature to 60℃-90℃, then increase the alkaline concentration by 0.1%-0.5% and the temperature by 10℃-20℃ every 1h, and continue pretreatment for 4.0h-7.0h, centrifuge the treated material, and wash the solid part with water to obtain a product with high cellulose content. 27.37g (97.49%) of high-purity cellulose can be obtained per 100g of absolute dry corn stover.

[0025] Specifically, in step 1, the composition of the corn stover raw material includes 36% to 41% cellulose, 19% to 24% hemicellulose, and 35% to 45% lignin and the like.

[0026] Specifically, in step 3, 100 g of absolute dried corn stover is treated with alkali to obtain 83.40 g of stover residue containing 36.98 g of cellulose, 18.78 g of hemicellulose, 27.64 g of lignin, etc.

[0027] Specifically, in step 4, 100 g of absolute dried corn stover is acid hydrolyzed to obtain 53.11 g of acid hydrolyzed stover residue and 1.53 L of xylose hydrolyzate. The acid hydrolyzed stover residue contains 34.32 g of cellulose and 18.79 g of lignin, etc., and the xylose in the xylose hydrolyzate has a concentration of 11.84 g / L and a purity of 74.14%.

[0028] Specifically, in step 5, 100 g of bone-dried corn stover can be subjected to stepwise alkali treatment to obtain 27.37 g (97.49%) of high-purity cellulose.

[0029] The method for extracting high-purity xylose liquid and cellulose using corn stover of the present invention will be further described below with reference to specific examples. Example 1: Alkaline treatment

[0030] In this embodiment, a four-factor, three-level response surface model optimization experiment was designed, and a total of 29 groups of experiments were performed. Three batches were verified through optimization using the response surface model. As a result, in the optimal experimental group, the cellulose retention rate was 95.53%, the hemicellulose retention rate was 91.57%, and the lignin removal rate was 32.22%. The optimal conditions for the alkali treatment were 0.1% NaOH solution, 1:6 solid-liquid ratio, and 1.2h incubation at 125°C. The composition ratio of the stem and leaf residue under the optimal conditions for the alkali treatment is shown in Table 1. Under these optimal conditions, theoretically, when 100g of absolute dry corn stems and leaves (about 38.71g of cellulose, about 20.51g of hemicellulose, about 40.78g of lignin, etc.) is alkali-treated, 83.40g of stem and leaf residue containing about 36.98g of cellulose, about 18.78g of hemicellulose, and about 27.64g of lignin, etc. can be obtained.

[0031] [Table 1]

[0032] Example 2: Acid hydrolysis In this example, a total of 29 groups of experiments were carried out, and the specific experimental plans and results are shown in Table 3. Three batches were verified through the optimization of the response surface model, and the optimal experimental group showed a xylose yield of 84.51%, a cellulose retention rate of 92.80%, a hemicellulose retention rate of 0%, and a lignin removal rate of 32.01%. The optimal conditions for acid hydrolysis were a 2.49% concentration H2SO4 solution, a 1:12 solid-liquid ratio, and incubation at 124.8°C for 1.58 hours. The composition ratio of the acid hydrolyzed stem and leaf residue under the optimal conditions for acid hydrolysis is shown in Table 2. Under these optimal conditions, theoretically, 100 g of absolutely dried corn stover (about 38.71 g of cellulose, about 20.51 g of hemicellulose, about 40.78 g of lignin, etc.) is subjected to a first dilute alkali treatment and then hydrolyzed with dilute acid to obtain 53.11 g of acid hydrolyzed stover residue containing about 34.32 g of cellulose and about 18.79 g of lignin, etc.

[0033] [Table 2]

[0034] [Table 3]

[0035] Example 3: Comparison of xylose hydrolyzate obtained by directly treating corn stover with acid and xylose hydrolyzate obtained by subjecting corn stover to alkali treatment and acid hydrolysis A liquid phase test of xylose purity was performed on xylose hydrolyzate liquid 1 obtained by hydrolysis under the optimal treatment conditions optimized in Examples 1 and 2, and xylose hydrolyzate liquid 2 obtained by direct acid treatment.The results showed that the xylose purity of xylose hydrolyzate liquid 1 obtained by alkali treatment-acid hydrolysis was 74.14%, while the xylose purity of xylose hydrolyzate liquid 2 obtained by direct acid treatment was only 62.16%.

[0036] Example 4: Extraction of high-purity cellulose by further stepwise alkaline treatment of stem and leaf residue obtained by alkaline-acid treatment In this example, the acid hydrolyzed stem and leaf residue (cellulose content 64.62%, hemicellulose content 0%, lignin etc. 35.38%) is further treated with alkali to remove components such as lignin in the acid hydrolyzed stem and leaf residue, thereby improving the cellulose content in the stem and leaf residue.

[0037] (1) Effect of initial alkali application on cellulose content in acid hydrolyzed stem and leaf waste Pretreatment conditions: the ratio of acid hydrolyzed stem and leaf waste to purified water is 1:8, the initial reaction temperature is 90°C, the temperature is increased by 20°C per hour, 0.5% alkali is added, and the reaction time is 4h. The effect of the initial amount of alkali NaOH on improving the cellulose content in the acid hydrolyzed stem and leaf waste was investigated, and the initial alkali concentration ratios are (1) 0.2%, (2) 0.3%, (3) 0.4%, and (4) 0.5%. The corresponding results are shown in Table 4.

[0038] As can be seen from Table 4, when the ratio of the initial alkali concentration increases from 0.2% to 0.4%, the content of cellulose in the remaining residue nearly reaches a maximum of 89.97%, and the retention rate of cellulose is 70.97%.

[0039] [Table 4]

[0040] (2) Effect of initial reaction temperature on improving cellulose content in acid hydrolyzed stem and leaf waste Pretreatment conditions: the ratio of acid hydrolyzed stalk waste to water is 1:9, the initial alkali concentration is 0.4%, the temperature is increased by 20°C per hour, 0.5% alkali is added, and the reaction time is 4h. The effect of the initial temperature on the improvement of the cellulose content in the acid hydrolyzed stalk waste is investigated, and the reaction temperatures are (1) 60°C, (2) 70°C, (3) 80°C, and (4) 90°C, respectively. The corresponding results are shown in Table 5.

[0041] As can be seen from Table 5, the cellulose content tends to increase approximately when the reaction temperature increases from 60° C. to 90° C. When the initial reaction temperature is 90° C., the cellulose content in the remaining residue is up to 91.10%, and the cellulose retention rate is 66.83%.

[0042] [Table 5]

[0043] (3) Effect of reaction time on the cellulose content in acid-hydrolyzed stem and leaf residues Pretreatment conditions: the ratio of acid hydrolyzed stalk residue to purified water was 1:12, the initial alkali concentration was 0.4%, the initial temperature was 90°C, the temperature was increased by 20°C per hour, and 0.5% alkali was added to study the effect of reaction time on improving the cellulose content in acid hydrolyzed stalk residue, the reaction times were (1) 4h, (2) 5h, (3) 6h, and (4) 7h, respectively. The corresponding results are shown in Table 6.

[0044] As can be seen from Table 6, when the reaction time increases from 4 to 6 hours, the cellulose content generally tends to increase. When the reaction time is 6 hours, the cellulose content in the acid hydrolyzed stem and leaf residue is up to 97.63%, and the cellulose retention rate is 66.23%.

[0045] [Table 6]

[0046] Example 5 Extraction of high purity xylose hydrolysate and cellulosic products (small scale) from corn stover involves the following steps.

[0047] Step 11 Raw material selection: Select and use corn stover raw material with a moisture content of 7%.

[0048] Step 12 Raw material pretreatment: Corn stalks and leaves are crushed in a crusher, and the particles with a particle size of 60 to 300 mesh are screened out. They are then placed in a ventilation drying box and dried at 45°C for 22 hours. The moisture content is measured and found to be less than 0.5% (absolutely dry material).

[0049] Step 13 Alkaline treatment: 100g of crushed and dried corn stover was weighed, mixed with 600g of process water, and 30% concentrated NaOH solution was added to adjust the NaOH concentration of the system to 0.1%, packed into a sealed blue-cap bottle, placed in a sterilized pot, heated to 125℃ and kept warm for 2h, cooled after heating, centrifuged to separate the solid-liquid phase from the material, washed the solid part with 1L of clean water, centrifuged the solid-liquid phase again, washed twice, and measured the wet weight of the solid part was 333.6g (82.27g on a dry basis). Its dry basis composition was measured and found to contain about 35.98g of cellulose, about 18.98g of hemicellulose, and about 27.31g of lignin, etc.

[0050] Step 14 Acid hydrolysis: 736g of 2.5% H2SO4 solution was added to the entire solid obtained in step 3, packed into a sealed blue-cap bottle, placed in a sterilized pot, heated to 100°C and kept warm for 30 minutes, cooled after the end of the warming, centrifuged to separate the solid-liquid phase from the material, and 910g of liquid was obtained. A liquid phase test showed that xylose had a concentration of 12.56g / L and a purity of 75.23%. The solid portion was washed with 1L of clean water, and the solid-liquid phase was centrifuged and washed twice to obtain a solid portion with a wet weight of 183.78g (52.01g on a dry basis). The composition was measured and found to be 34.77g cellulose and 17.24g lignin.

[0051] Step 15 Stepwise alkali treatment: add 225g of process water to the solid part obtained in step 4, adjust the NaOH concentration in the system with 30% concentrated alkali solution to make the initial concentration 0.2%, fill into a sealed blue cap bottle, put into a sand bath pot and keep warm, set the initial temperature to 60℃, heat and keep warm for 1h, add 30% alkali solution into the blue cap bottle to increase the alkali concentration of the system by 0.5%, and increase the temperature by 10℃, in this way, increase the alkali concentration of the system by 0.5% every 1h, increase the temperature to 10℃, react for a total of 4h, cool, centrifuge the solid-liquid phase from the sample, wash the solid part with 1L of water 3 times, and then bake the solid part in an oven at 65℃ for 20h, obtain 27.19g of dried product, which is tested and found to have a cellulose purity of 96.93%.

[0052] Example 6 Extraction of high purity xylose hydrolysate and cellulose products from corn stover includes the following steps.

[0053] Step 21 Raw material selection: Corn stover raw material with a moisture content of 13% is selected and used.

[0054] Step 22 Raw material pretreatment: Corn stalks and leaves are crushed in a crusher, and the particles with a particle size of 60 to 300 mesh are screened out. They are then placed in a ventilation drying box and dried at 45°C for 26 hours. The moisture content is measured and found to be less than 0.5% (absolutely dry material).

[0055] Step 23 Alkali treatment: 10 kg of crushed and dried corn stover was weighed, mixed with 60 kg of process water, and 30% concentrated NaOH solution was added to adjust the NaOH concentration of the system to 0.4%. The mixture was mixed uniformly and placed in a pressure reactor (acid-alkali resistant), heated to 85°C and kept at 85°C for 1.2 hours. After heating, the mixture was cooled and the solid-liquid phase was centrifuged from the material. The solid portion was washed with 50 L of fresh water. The solid-liquid phase was centrifuged and washed twice to obtain a solid portion with a wet weight of 33.5 kg (8.3 kg on a dry basis). The composition of the solid portion on a dry basis was measured and found to contain approximately 3.6 kg of cellulose, approximately 1.9 kg of hemicellulose, and approximately 2.8 kg of lignin.

[0056] Step 24 Acid hydrolysis: 74.5 kg of 1.0% H2SO4 solution was added to all the solids obtained in step 3 and mixed uniformly, then placed in a pressure reactor (acid-alkali resistant), heated to 160°C and kept for 120 min, cooled after the end of the keeping, centrifuged to separate the solid-liquid phase from the material, and 90.7 kg of liquid was obtained. When the liquid phase test was performed, xylose had a concentration of 11.96 g / L and a purity of 73.23%. The solid part was washed with 30 L of clean water, and the solid-liquid phase was centrifuged and washed twice to obtain a solid part with a wet weight of 18.9 kg (5.6 kg on a dry basis). The composition was measured and found to be 3.7 kg cellulose and 1.8 kg lignin.

[0057] Step 25 Stepwise alkali treatment: add 23.1 kg of process water to the solid part obtained in step 4, adjust the NaOH concentration in the system with 30% concentrated alkali solution to make the initial concentration 1%, mix uniformly, put into a pressure reactor (acid-alkali resistance), connect the reactor to a pump line and a refill bolt, refill with 30% alkali solution. Set the initial temperature to 90 ° C, heat and keep warm for 1 h, add 30% alkali solution to increase the alkali concentration of the system by 0.1%, increase the temperature by 20 ° C, in this way, increase the alkali concentration of the system by 0.1% every 1 h, increase the temperature by 20 ° C, react for a total of 7 h, cool, separate the solid-liquid phase from the product by centrifugation, wash the solid part with 30 L of water three times, then bake the solid part at 65 ° C for 20 h, obtain 2.82 kg of dried product, which is tested and found to have a cellulose purity of 95.73%.

[0058] Example 7 Extraction of high purity xylose hydrolysate and cellulose products from corn stover includes the following steps.

[0059] Step 31 Raw material selection: Select and use corn stover raw material with a moisture content of 10%.

[0060] Step 32 Raw material pretreatment: Corn stalks and leaves are crushed in a grinder, and the particles with a particle size of 60 to 300 mesh are screened out. They are then placed in an air-dried box and dried at 45°C for 25 hours. The moisture content is measured and found to be less than 0.5% (absolutely dry material).

[0061] Step 33 Alkali treatment: 10 kg of crushed and dried corn stover was weighed, mixed with 70 kg of process water, and 30% concentrated NaOH solution was added to adjust the NaOH concentration of the system to 0.4%. The mixture was mixed uniformly and placed in a pressure reactor (acid-alkali resistant), heated to 122°C and kept warm for 90 minutes. After heating, the mixture was cooled and the solid-liquid phase was centrifuged from the material. The solid portion was washed with 50 L of fresh water. The solid-liquid phase was centrifuged and washed twice to obtain a solid portion with a wet weight of 31.5 kg (8.1 kg on a dry basis). The composition of the solid portion on a dry basis was measured and found to contain about 3.7 kg of cellulose, about 1.9 kg of hemicellulose, and about 2.5 g of lignin, etc.

[0062] Step 34 Acid hydrolysis: 72.5 kg of 1.6% H2SO4 solution was added to the entire solid obtained in step 3, mixed uniformly, and placed in a pressure reactor (acid-alkali resistant), heated to 110°C and kept for 120 min. After the end of the keeping, the temperature was lowered, and the solid-liquid phase was centrifuged from the material to obtain 88.7 kg of liquid. When the liquid phase test was performed, the xylose had a concentration of 11.86 g / L and a purity of 74.28%. The solid part was washed with 30 L of clean water, and the solid-liquid phase was centrifuged and washed twice to obtain a solid part with a wet weight of 20.9 kg (6.4 kg on a dry basis). The composition was measured to be 3.8 kg cellulose, 0.3 kg hemicellulose, and 2.3 kg lignin.

[0063] Step 35 Stepwise alkali treatment: add 28 kg of process water to the solid part obtained in step 4, adjust the NaOH concentration in the system with 30% concentrated alkali solution to make the initial concentration 0.5%, mix uniformly, put into a pressure reactor (acid-alkali resistant), connect the reactor to a pump line and a refill bolt, and refill with 30% alkali solution. Set the initial temperature to 80°C, heat and keep warm for 1h, add 30% alkali solution to increase the alkali concentration of the system by 0.3%, and increase the temperature by 15°C, in this way, increase the alkali concentration of the system by 0.3% every 1h, increase the temperature by 15°C, react for a total of 6h, cool, separate the solid-liquid phase from the product by centrifugation, wash the solid part with 30L of water three times, and then bake the solid part at 65°C for 20h, obtain 2.42 kg of dried product, which is tested and found to have a cellulose purity of 98.79%.

[0064] The above are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for extracting high-purity xylose liquid and cellulose using corn stover, comprising the steps of: Step 1: selecting and using corn stover raw material with a moisture content of 7% to 13%; Step 2: raw material pretreatment: first, pulverize the corn stover into powder with a particle size of 60 mesh to 300 mesh using a grinder, then put it into a ventilation drying box and dry it at 45°C for 22h to 26h to obtain absolutely dry powdered corn stover; Alkaline treatment: mixing the absolute dry powdered corn stover obtained in step 2 with process water, adjusting the NaOH concentration in the system to 0.1%-0.4% with a 30% concentrated alkaline solution, and carrying out alkaline treatment at a temperature of 85°C-125°C for 1.2h-2.0h, followed by centrifugation to obtain stover residue and centrifugal supernatant, and subjecting the stover residue to a xylose extraction process; Acid hydrolysis: The stem and leaf residue obtained in step 3 was mixed with 1.0% to 2.5% diluted H ２ SO ４ Step 4: mixing the above in a predetermined ratio, hydrolyzing the mixture at 100°C to 160°C for 30 to 120 minutes, and then centrifuging the mixture to obtain an acid hydrolyzed liquid and an acid hydrolyzed stem and leaf residue; converting the acid hydrolyzed liquid into a high-purity xylose liquid; and subjecting the acid hydrolyzed stem and leaf residue to a cellulose extraction step; and step 5, comprising: step 4, mixing the acid hydrolyzed stem and leaf residue obtained in step 4 with process water, adjusting the NaOH concentration in the system with 30% concentrated alkali solution, with an initial concentration of 0.2%-1%, and an initial temperature of 60°C-90°C, and then increasing the alkali concentration by 0.1%-0.5% and the temperature by 10°C-20°C every 1 h, and continuing the pretreatment for 4.0 h-7.0 h, centrifuging the treated material, and washing the solid part with water to obtain a product with high cellulose content.

2. The method for extracting high-purity xylose liquid and cellulose using corn stover according to claim 1, characterized in that in step 1, the composition of the corn stover raw material comprises 36% to 41% cellulose, 19% to 24% hemicellulose, and 35% to 45% lignin, etc.

3. 2. The method for extracting high-purity xylose liquid and cellulose using corn stover as claimed in claim 1, characterized in that in step 3, 100 g of absolute dried corn stover is treated with alkali to obtain 83.40 g of stover residue containing 36.98 g of cellulose, 18.78 g of hemicellulose, and 27.64 g of lignin, etc.

4. In step 4, 100 g of bone-dried corn stover was acid hydrolyzed to obtain 53.11 g of acid hydrolyzed stover residue and 1.53 L of xylose hydrolyzate; The method for extracting high-purity xylose liquid and cellulose using corn stover as described in claim 1, characterized in that the acid hydrolyzed stover residue contains 34.32 g of cellulose and 18.79 g of lignin, etc., and the concentration of xylose in the xylose hydrolyzed liquid is 11.84 g / L.

5. 2. The method for extracting high-purity xylose liquid and cellulose using corn stover according to claim 1, wherein in step 5, 100 g of absolute dry corn stover is subjected to stepwise alkali treatment to obtain 27.37 g of high-purity cellulose.

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