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 particularly relates to a method for extracting high-purity xylose liquid and cellulose using corn stover. [Background technology]

[0002] Lignocellulosic feedstocks can be obtained from a variety of sources, including agricultural residues, forest crops, and industrial residues. Corn stover, a type of agricultural residue, is abundant, inexpensive, safe, and renewable, making it a viable alternative to fossil fuels. The three main components of stover biomass feedstock—cellulose, hemicellulose, and lignin—can be converted into various forms of high-value chemicals, mitigating environmental problems and promoting economic and social development. However, because the various components in corn stover are closely interconnected, separating and purifying them for further value creation is difficult. Currently, most stover biomass is directly incinerated or disposed of. Designing appropriate processing methods is urgently needed to effectively improve the utilization rate of the feedstock.

[0003] Currently, the separation of the three components of stover mainly involves directly treating agricultural waste with acidic solution or xylanase to hydrolyze or enzymatically hydrolyze the hemicellulose component 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 not yet been resolved.

[0004] Problem 1: When corn stover is acid-hydrolyzed to obtain a hydrolyzate, the composition of the hydrolyzate is relatively complex and the purity of xylose is low, which affects the subsequent purification of xylose.

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

[0006] Problem 3: The waste residue obtained by acid hydrolysis has a low cellulose content and is of low value.

[0007] The cellulose content of 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 solution, and then treated with hemicellulase to convert more than 45% of the hemicellulose into a xylose solution, resulting in a cellulose residue with a cellulose content of only 76.03%. The cellulose residue is then fermented with commercially available cellulase and alcohol-activated dry yeast to produce fuel ethanol, but only 0.522g of ethanol is obtained per 1g of cellulose, 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 acid hydrolyzed to extract pentoses, 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 76.03% or less. Summary of the Invention [Problem to be solved by the invention]

[0008] The technical problem to be solved by the present invention 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 process cost. [Means for solving the problem]

[0009] The present invention is achieved as follows.

[0010] Step 1: Select and use corn stover raw materials with a moisture content of 7% to 13%; Step 2: raw material pretreatment: first, corn stover is crushed into powder with a particle size of 60 mesh to 300 mesh using a grinder, and then placed in a blast drying box and dried at 45°C for 22 to 26 hours to obtain absolutely dry powdered corn stover; Alkali 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 1.2 hours-2.0 hours, followed by centrifugation to obtain a stover residue and a centrifugal supernatant, and the stover residue is supplied to a xylose extraction step; Acid hydrolysis: Mix the stem and leaf residue obtained in step 3 with 1.0% to 2.5% diluted H2SO4 in a predetermined ratio, acid hydrolyze at 100°C to 160°C for 30 to 120 minutes, and then centrifugate to obtain an acid hydrolyzed liquid and 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% to 1%, setting the initial temperature at 60°C to 90°C, and then increasing the alkali concentration by 0.1% to 0.5% every hour, raising the temperature by 10°C to 20°C, and maintaining this temperature for 4.0 to 7.0 hours. The treated material is centrifuged, and the solid portion is washed with water to obtain a product with a high cellulose content. [Effects 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 also 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 corn stover.

[0013] 2. After dilute alkali treatment, the corn stover is subjected to dilute acid hydrolysis, which hydrolyzes the hemicellulose in the corn stover to convert it to xylose (conversion rate 77.4%), yielding a clear hydrolyzate with few impurities from which xylose can be easily separated. Because both dilute alkali and dilute acid treatments are performed only once, eliminating the need for multi-stage treatments, the process is simplified, with the dilute alkali concentration used being only 0.1% (mass percent) and the dilute sulfuric acid concentration being 2.49% (mass percent).

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

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

[0016] 2. The xylose hydrolyzate obtained by acid hydrolysis of corn stover to extract xylose is not highly pure 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, at less than 76.03%. DETAILED DESCRIPTION OF THE INVENTION

[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 comprises the following steps:

[0020] Step 1 Raw material selection: Corn stover raw material with a moisture content of 7% to 13% is selected and used.

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

[0022] Step 3 Alkali 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 a 30% concentrated alkaline solution. The system is then subjected to alkaline treatment at a temperature of 85°C-125°C for 1.2-2.0 hours, after which the mixture is centrifuged to obtain a stover residue and a centrifugal supernatant, which is then fed to the xylose extraction process. When 100g of corn stover is processed, 80.75g of residual solids are obtained, with a xylose loss rate of less than 5% and a cellulose loss rate of 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. The mixture is then centrifuged to obtain an acid hydrolyzed solution and acid hydrolyzed stem and leaf residue. The acid hydrolyzed solution is then subjected to the xylose extraction process to produce xylose. The acid hydrolyzed solution is converted into a high-purity xylose solution, and the acid hydrolyzed stem and leaf residue is then subjected to the cellulose extraction process. After subjecting 100 g of raw stem and leaf to steps 2, 3, and 4, 53.11 g of acid hydrolyzed stem and leaf residue and 1.53 L of xylose hydrolyzed solution are obtained. The acid hydrolyzed stem and leaf residue contains 34.32 g of cellulose and 18.79 g of lignin, etc. The xylose in the xylose hydrolyzed solution 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 from Step 4 with process water in the specified ratio, a 30% concentrated alkaline solution is added to adjust the NaOH concentration in the system. The initial concentration is 0.2%-1% and the initial temperature is 60-90°C. The alkaline concentration is then increased by 0.1%-0.5% and the temperature is increased by 10-20°C every hour for 4.0-7.0 hours. The treated material is then centrifuged and the solid portion is washed with water to obtain a product with a high cellulose content. 27.37g (97.49%) of high-purity cellulose is obtained per 100g of dried corn stover.

[0025] Specifically, in step 1, the corn stover raw material has a composition including 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 dry 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 was acid hydrolyzed to obtain 53.11 g of acid hydrolyzed stover residue and 1.53 L of xylose hydrolyzate. The acid hydrolyzed stover residue contained 34.32 g of cellulose and 18.79 g of lignin, etc., and the xylose in the xylose hydrolyzate had 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 is subjected to stepwise alkali treatment to obtain 27.37 g (97.49%) of high-purity cellulose.

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

[0030] In this example, a four-factor, three-level response surface model optimization experiment was designed. A total of 29 experiments were conducted. Three batches of validation were performed using the response surface model. The optimal experimental group achieved 95.53% cellulose retention, 91.57% hemicellulose retention, and 32.22% lignin removal. The optimal conditions for alkaline treatment were a 0.1% NaOH solution, a 1:6 solid-liquid ratio, and incubation at 125°C for 1.2 hours. The composition of the corn stover residue under the optimal alkaline treatment conditions is shown in Table 1. Under these optimal conditions, the theoretical yield of 83.40 g of corn stover residue containing approximately 36.98 g cellulose, 18.78 g hemicellulose, and 27.64 g lignin was obtained by alkaline treatment of 100 g of absolute dry corn stover (approximately 38.71 g cellulose, 20.51 g hemicellulose, and 40.78 g lignin).

[0031] [Table 1]

[0032] Example 2: Acid Hydrolysis In this example, a total of 29 experiments were conducted, with the specific experimental design and results shown in Table 3. Three batches were tested using response surface model optimization. The optimal experimental group achieved 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% H2SO4 solution, a 1:12 solid-liquid ratio, and incubation at 124.8°C for 1.58 hours. The composition of the acid hydrolyzed stem and leaf residue under the optimal conditions is shown in Table 2. Under these optimal conditions, theoretically, 100 g of absolute dry corn stover (approximately 38.71 g of cellulose, approximately 20.51 g of hemicellulose, and approximately 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 approximately 34.32 g of cellulose and approximately 18.79 g of lignin, etc.

[0033] [Table 2]

[0034] [Table 3]

[0035] Example 3: Comparison of xylose hydrolyzate obtained by direct acid treatment of corn stover with xylose hydrolyzate obtained by alkali treatment and acid hydrolysis of corn stover A liquid phase test of xylose purity was performed on xylose hydrolyzed solution 1 obtained by hydrolysis under the optimal treatment conditions optimized in Examples 1 and 2, and xylose hydrolyzed solution 2 obtained by direct acid treatment.The results showed that the xylose purity of xylose hydrolyzed solution 1 obtained by alkali treatment-acid hydrolysis was 74.14%, while the xylose purity of xylose hydrolyzed solution 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, 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 from 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 the improvement of cellulose content in acid-hydrolyzed stem and leaf residues Pretreatment conditions were: acid hydrolyzed stem and leaf residue: 1:8 ratio, initial reaction temperature 90°C, temperature increase 20°C per hour, alkali addition 0.5%, reaction time 4 h. The effect of the initial alkali NaOH concentration on improving the cellulose content in acid hydrolyzed stem and leaf residue was investigated. The initial alkali concentration ratios were (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 initial alkali concentration increases from 0.2% to 0.4%, the content of cellulose in the remaining residue reaches almost the 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 residue Pretreatment conditions were: the ratio of acid hydrolyzed stem and leaf residue to water was 1:9, the initial alkali concentration was 0.4%, the temperature was increased by 20°C per hour, 0.5% alkali was added, and the reaction time was 4 h. The effect of the initial temperature on improving the cellulose content in the acid hydrolyzed stem and leaf residue was investigated. The reaction temperatures were (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 substantially as the reaction temperature increases from 60 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 of acid-hydrolyzed stem and leaf residue Pretreatment conditions were: acid hydrolyzed stover residue to purified water ratio 1:12, initial alkali concentration 0.4%, initial temperature 90°C, temperature increase 20°C per hour, alkali addition 0.5%. The effect of reaction time on improving the cellulose content in acid hydrolyzed stover residue was investigated. The reaction times were (1) 4 h, (2) 5 h, (3) 6 h, and (4) 7 h, respectively. The corresponding results are shown in Table 6.

[0044] As can be seen from Table 6, the cellulose content generally increases as the reaction time increases from 4 to 6 hours. 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: Corn stover raw material with a moisture content of 7% is selected and used.

[0048] Step 12 Raw material pretreatment: Corn stover is crushed in a crusher, and the particles with a particle size of 60 to 300 mesh are screened out. The particles 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 Alkali treatment: 100g of crushed and dried corn stover was weighed and mixed with 600g of process water. 30% concentrated NaOH solution was added to adjust the NaOH concentration of the system to 0.1%. The mixture was then packed into a sealed blue-cap bottle, placed in a sterilized pot, heated to 125°C and kept at that temperature for 2 hours, and cooled. The solid-liquid phase was centrifuged and the solid portion was washed with 1L of clean water. The solid-liquid phase was centrifuged and washed twice. The wet weight of the solid portion was 333.6g (82.27g dry weight). The dry weight composition of the solid portion was determined to be approximately 35.98g of cellulose, 18.98g of hemicellulose, and 27.31g of lignin.

[0050] Step 14 Acid hydrolysis: 736 g of 2.5% H2SO4 solution was added to the entire solid obtained in Step 3, packed into a sealed blue-cap bottle, and placed in a sterilized pot. The mixture was heated to 100°C and held for 30 minutes. After the incubation period, the mixture was cooled and the solid-liquid phase was centrifuged to separate the material. 910 g of liquid was obtained. Liquid phase testing revealed a xylose concentration of 12.56 g / L and a purity of 75.23%. The solid was washed with 1 L of clean water, and the solid-liquid phase was centrifuged and washed twice more to obtain a solid weighing 183.78 g (52.01 g dry). The composition was determined to be 34.77 g of cellulose and 17.24 g of lignin.

[0051] Step 15 Stepwise alkali treatment: 225g of process water was added to the solid fraction obtained in step 4, and the NaOH concentration in the system was adjusted with 30% concentrated alkali solution to an initial concentration of 0.2%. The mixture was then packed into a sealed blue-capped bottle and heated in a sand bath. The initial temperature was set to 60°C, and the mixture was heated and kept warm for 1 hour. 30% alkali solution was added to the blue-capped bottle to increase the alkali concentration of the system by 0.5%, and the temperature was raised by 10°C. This process was continued every hour to increase the alkali concentration of the system by 0.5%, and the temperature was raised to 10°C. A total of 4 hours of reaction was allowed to proceed, after which the solid-liquid phase was separated by centrifugation. The solid fraction was washed with 1L of water three times, and then baked in an oven at 65°C for 20 hours. 27.19g of dried product was obtained, which was 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 stover is crushed in a crusher, and the particles with a particle size of 60 to 300 mesh are screened out. The particles 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 and mixed with 60 kg of process water. 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). The mixture was heated to 85°C and kept at that temperature for 1.2 hours. After heating, the mixture was cooled and the solid-liquid phase was separated by centrifugation. The solid portion was washed with 50 L of clean water. The solid-liquid phase was then 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 dry composition of the solid portion was determined to contain approximately 3.6 kg of cellulose, 1.9 kg of hemicellulose, and 2.8 kg of lignin.

[0056] Step 24 Acid hydrolysis: 74.5 kg of 1.0% H2SO4 solution was added to the entire solid obtained in Step 3 and mixed uniformly. The mixture was then placed in a pressure reactor (acid-alkali resistant), heated to 160°C, and maintained for 120 minutes. After the incubation period, the mixture was cooled and the solid-liquid phase was centrifuged to separate the material. 90.7 kg of liquid was obtained. Liquid phase testing revealed a xylose concentration of 11.96 g / L and a purity of 73.23%. The solid was washed with 30 L of clean water, and the solid-liquid phase was centrifuged and washed twice, yielding a solid with a wet weight of 18.9 kg (5.6 kg dry weight). The composition was determined to be 3.7 kg of cellulose and 1.8 kg of lignin.

[0057] Step 25 Stepwise alkali treatment: Add 23.1 kg of process water to the solid fraction obtained in step 4, adjust the NaOH concentration in the system with 30% concentrated alkali solution to make the initial concentration 1%, mix uniformly, and place in a pressure reactor (acid-alkali resistant). Connect the reactor to a pump line and a refill bolt to add 30% alkali solution. Set the initial temperature to 90 ° C, heat and maintain for 1 hour, add 30% alkali solution to increase the alkali concentration of the system by 0.1%, and increase the temperature by 20 ° C. In this way, increase the alkali concentration of the system by 0.1% every hour, increase the temperature by 20 ° C., and react for a total of 7 hours. Cool, separate the solid-liquid phase from the product by centrifugation, wash the solid fraction with 30 L of water three times, and then bake at 65 ° C for 20 hours to obtain 2.82 kg of dried product, which was 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: Corn stover raw material with a moisture content of 10% is selected and used.

[0060] Step 32 Raw material pretreatment: Corn stalks 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 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 and mixed with 70 kg of process water. 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). The mixture was heated to 122°C and kept at that temperature for 90 minutes. After heating, the mixture was cooled and the solid-liquid phase was separated by centrifugation. The solid portion was washed with 50 L of clean water. The solid-liquid phase was then 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 dry composition of the solid portion was determined to contain approximately 3.7 kg of cellulose, 1.9 kg of hemicellulose, and 2.5 g of lignin.

[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). The mixture was heated to 110°C and maintained for 120 minutes. After the incubation period, the temperature was lowered. The solid-liquid phase was centrifuged to separate the material, yielding 88.7 kg of liquid. Liquid phase testing revealed a xylose concentration of 11.86 g / L and a purity of 74.28%. The solid was washed with 30 L of clean water, and the solid-liquid phase was centrifuged and washed twice, yielding a solid with a wet weight of 20.9 kg (6.4 kg dry weight). The composition was determined to be 3.8 kg of cellulose, 0.3 kg of hemicellulose, and 2.3 kg of lignin.

[0063] Step 35 Stepwise alkali treatment: Add 28 kg of process water to the solid fraction obtained in step 4, adjust the NaOH concentration in the system with 30% concentrated alkali solution to an initial concentration of 0.5%, mix uniformly, and place in a pressure reactor (acid-alkali resistant). Connect the reactor to a pump line and a refill bolt to add 30% alkali solution. Set the initial temperature to 80°C, heat and maintain for 1 hour, add 30% alkali solution to increase the alkali concentration of the system by 0.3%, and increase the temperature by 15°C. In this manner, increase the alkali concentration of the system by 0.3% every hour, and increase the temperature by 15°C for a total of 6 hours. Cool, separate the solid-liquid phase from the product by centrifugation, wash the solid fraction with 30 L of water three times, and then bake at 65°C for 20 hours to obtain 2.42 kg of dried product. Test results showed that the cellulose purity was 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: Step 1: selecting and using corn stover raw material with a moisture content of 7% to 13%; Step 2: raw material pretreatment: first, corn stover is ground into powder with a particle size of 60-300 mesh using a grinder, and then placed in a ventilated drying box and dried at 45°C for 22-26 hours to obtain absolutely dry powdered corn stover; Alkali 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 alkali solution, and carrying out alkali treatment at a temperature of 85°C-125°C for 1.2 hours-2.0 hours, followed by centrifugation to obtain a stover residue and a centrifugal supernatant, and subjecting the stover residue to a xylose extraction step; 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 ingredients in a predetermined ratio, acid hydrolyzing the mixture at 100°C to 160°C for 30 to 120 minutes, and then centrifuging the mixture to obtain an acid hydrolyzed solution and acid hydrolyzed stem and leaf residue; converting the acid hydrolyzed solution into a high-purity xylose solution, and subjecting the acid hydrolyzed stem and leaf residue to a cellulose extraction step; and step 5, a stepwise alkali treatment: mixing the acid hydrolyzed stem and leaf 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% to 1% and an initial temperature of 60°C to 90°C, and then increasing the alkali concentration by 0.1% to 0.5% and the temperature by 10°C to 20°C every hour, for a duration of 4.0 to 7.0 hours. The treated material is centrifuged, and the solid portion is washed with water to obtain a product with a high cellulose content.

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

3. 2. The method for extracting high-purity xylose solution and cellulose using corn stover according to claim 1, wherein 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.

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