CN112442519A

CN112442519A - Method for pretreating corn straw and corn straw pretreatment

Info

Publication number: CN112442519A
Application number: CN201910839027.2A
Authority: CN
Inventors: 岳军; 宁艳春; 王硕; 徐友海; 胡世洋; 屈海峰; 岳春雨; 惠继星; 金刚; 谢宝华
Original assignee: Petrochina Co Ltd
Current assignee: Petrochina Co Ltd
Priority date: 2019-09-05
Filing date: 2019-09-05
Publication date: 2021-03-05
Anticipated expiration: 2039-09-05
Also published as: CN112442519B

Abstract

The invention discloses a method for pretreating corn straws and a corn straw pretreatment substance. Wherein, the method comprises the following steps: mixing the crushed corn straws with a trisodium phosphate solution, and then cooking and carrying out enzymatic saccharification on the obtained mixture. By applying the technical scheme of the invention, the corn straw is treated by using the trisodium phosphate solution, and the dosage of the trisodium phosphate can realize a better pretreatment effect under the condition of lower concentration, so that the wastewater can be more easily treated due to the reduction of the dosage of the trisodium phosphate, and the pretreatment cost can be effectively reduced.

Description

Method for pretreating corn straw and corn straw pretreatment

Technical Field

The invention relates to the technical field of chemical engineering, in particular to a method for pretreating corn straws and a corn straw pretreatment object.

Background

China is a big agricultural country, lignocellulose biomass resources represented by crop straws are rich, the total output exceeds 7 hundred million tons, the corn straws account for 36.7 percent, and the corn straws effectively utilize the cellulose resources and have practical significance on the energy crisis faced by human beings.

The main components constituting the lignocellulosic material include: cellulose, hemicellulose and lignin. During long-term natural evolution, green plants form cell walls that prevent microbial and enzymatic degradation, and cellulose is tightly packed with hemicellulose and lignin to form structures such as "reinforced concrete". Due to the protective effect of lignin and hemicellulose on cellulose and the crystal structure of cellulose, when the corn straw cellulose raw material is directly hydrolyzed, the hydrolysis degree is very low. The particular structural composition of lignocellulosic materials determines the complexity of the ethanol production process: some pre-treatment is required to break the cell wall barrier against microbial degradation, increasing the enzymatic efficiency of the cellulase. The main functions of the pretreatment are to degrade lignin, destroy the crystal structure of cellulose, increase the porosity and specific surface area of biomass and increase the accessibility of cellulase to cellulose, thereby improving the degradation rate of a substrate. Thus, pretreatment is an essential and crucial step in the biorefinery of lignocellulosic feedstocks.

The existing pretreatment methods mainly comprise various methods such as physical, chemical, biological and the like, or a combination of the methods, wherein the chemical method and the physical method are the research focus of researchers in various countries. The chemical pretreatment mainly uses alkali, inorganic acid, organic solvent, oxidant and the like as pretreatment reagents. In the organic solvent pretreatment process, the use of an organic solvent or a mixed solution of an organic solvent and an inorganic acid catalyst may break the connecting bonds between lignin and hemicellulose inside the fiber raw material. However, the pretreatment process, while significantly improving the degradability of the cellulosic material, also increases the complexity, equipment investment, and production costs of the overall production process. In addition, the various chemicals used in the pretreatment process also add difficulty and environmental threats to the subsequent treatment.

For example, the use of acidic or basic salts such as sulfites, phosphates, carbonates, etc. may also be used for the pretreatment of lignocelluloses. In patent CN 105063100 a, a method for pretreatment of non-wood fiber raw material by alkaline salt in combination with hydrogen peroxide is disclosed: soaking the non-wood fiber raw material in a mixed solvent, treating the non-wood fiber raw material at 50-120 ℃ for 1-6 h with a substrate concentration of 5-20 g/L, adding 0.5-2 times volume of deionized water after the reaction is finished, stirring the mixture at room temperature for 10-30 min to regenerate the cellulose raw material, and washing solid residues with water to finish the pretreatment process. The solid recovery rate after pretreatment is between 40 and 80 percent, the lignin removal rate is between 20 and 90 percent, the cellulose retention rate is between 75 and 95 percent, and the hemicellulose retention rate is between 70 and 90 percent. The pretreatment method effectively removes lignin, and largely retains cellulose and hemicellulose, thereby improving the enzymatic hydrolysis saccharification efficiency. Although the method achieves a good treatment effect, the use amount of the alkaline salt is large, the treatment time is long, the consumption amount of the pretreatment liquid in the treatment process is large, and hydrogen peroxide with strong oxidizability is added, so that the complexity of the process is increased to a certain extent, and the method also brings many problems to the treatment of the pretreatment liquid and has high cost. Because the pretreatment cost is one of the factors restricting the industrialization of the cellulosic ethanol, the pretreatment cost must be reduced while ensuring a good pretreatment effect.

Therefore, research and development of a low-cost, high-efficiency, environment-friendly and energy-saving pretreatment method is one of the keys for promoting the industrial development of bioethanol.

Disclosure of Invention

The invention aims to provide a method for pretreating corn straws and a corn straw pretreatment object, so as to provide a low-cost, high-efficiency, environment-friendly and energy-saving corn straw pretreatment process.

To achieve the above objects, according to one aspect of the present invention, there is provided a method of pretreating corn stover. The method comprises the following steps: mixing the crushed corn straws with a trisodium phosphate solution, and then cooking and carrying out enzymatic saccharification on the obtained mixture.

Furthermore, the water content of the corn straw for crushing is controlled below 15%.

Further, the corn stalks are crushed to be less than 2.8 mm.

Further, the trisodium phosphate solution is an aqueous solution prepared by adopting trisodium phosphate dodecahydrate; preferably, the concentration of the aqueous solution of trisodium phosphate is 4.3g/L to 33.0 g/L.

Further, when the crushed corn straws are mixed with a trisodium phosphate aqueous solution, the mass ratio of the trisodium phosphate aqueous solution to the corn straws is 15: 1-10: 1.

Further, the cooking comprises the steps of heating, heat preservation, cooling and water washing; preferably, the temperature is raised to 140-180 ℃ within 30-50 min; preferably, the heat preservation time is 30 min-1 h; preferably, the temperature is reduced to below 100 ℃ within 20-30 min.

Further, the enzyme used for enzymolysis and saccharification is a compound enzyme of cellulase and xylanase; preferably, the addition amount of the cellulase is 5-30 FPU/g substrate; preferably, the addition amount of the xylanase is 3-15 FXU/g substrate.

Further, the corn stalks are subjected to branch and leaf removal before being crushed.

Further, the corn stalks are crushed by a hammer crusher.

According to another aspect of the present invention, a corn stover pretreatment is provided. The corn straw pretreatment substance is obtained by adopting any one of the methods for pretreating corn straws by using sodium phosphate.

By applying the technical scheme of the invention, the corn straw is treated by using the trisodium phosphate solution, and the dosage of the trisodium phosphate can realize a better pretreatment effect under the condition of lower concentration, so that the wastewater can be more easily treated due to the reduction of the dosage of the trisodium phosphate, and the pretreatment cost can be effectively reduced.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:

FIG. 1 shows the corn stover reducing sugar yield after pretreatment at 140 ℃ in the examples; and

FIG. 2 shows the corn stover reducing sugar yield after pretreatment at 170 ℃ in the examples.

Detailed Description

It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings.

According to an exemplary embodiment of the present invention, a method for pretreating corn stover with sodium phosphate is provided. The method comprises the following steps: mixing the crushed corn straws with a trisodium phosphate solution, and then cooking and carrying out enzymatic saccharification on the obtained mixture.

The invention adopts trisodium phosphate to pretreat the corn straws, and can reduce the cost of pretreatment while ensuring the pretreatment effect. Of course, the method is not only suitable for corn straws, but also can be used for other lignocellulose raw materials under reasonable pretreatment conditions (under the guidance of the inventive concept of the invention, reasonable pretreatment conditions can be obtained through experimental exploration by a person skilled in the art). The industrial production can be realized by utilizing the existing mature equipment and devices. The pretreatment method can reduce the environmental and energy pressure and create economic value.

In the present invention, the moisture content of the corn stover used for the pulverization is controlled to 15% or less, and the moisture content is so low that the pulverization is difficult and the effect of the treatment is impaired. Preferably, the corn stalks are crushed to be less than 2.8mm, so that the subsequent enzymolysis is fully carried out.

According to an exemplary embodiment of the present invention, the trisodium phosphate solution is an aqueous solution prepared by using trisodium phosphate dodecahydrate, preferably, the concentration of the aqueous solution of trisodium phosphate is 4.3g/L to 33.0g/L, although higher or lower liquid-solid ratio is theoretically possible, but too high or too low liquid-solid ratio may cause increase of production cost or inconvenience in operation. In order to further control the cost and improve the convenience of operation, it is more preferable that the weight ratio of the trisodium phosphate solution to the corn stalks is 15: 1-10: 1 when the crushed corn stalks are mixed with the trisodium phosphate aqueous solution.

According to a typical embodiment of the present invention, cooking comprises the steps of heating, keeping warm, cooling and washing with water; preferably, the temperature is raised to 140-180 ℃ within 30-50 min, because shorter and longer temperature raising time can affect the treatment effect, mainly reflected in excessive removal of hemicellulose and reduction of reducing sugar yield. Preferably, the heat preservation time is 30 min-1 h, and shorter and longer time can affect the yield of reducing sugar; preferably, the temperature is reduced to below 100 ℃ within 20-30 min, the solid recovery rate is reduced due to overlong temperature reduction time, and the operation difficulty is higher due to overlong time.

According to a typical embodiment of the invention, the enzyme used for enzymatic saccharification is a compound enzyme of cellulase and xylanase; preferably, the cellulase is added in an amount of 20FPU/g substrate; preferably, the xylanase is added in an amount of 10FXU/g substrate.

In an embodiment of the invention, in the process of saccharifying the treated corn straws, the adopted enzyme is a solid enzyme preparation, the ratio of the filter paper enzyme activity to the beta-glucosaccharase enzyme activity is 4:1, the saccharifying temperature is 50 ℃, the time is 72 hours, and the substrate concentration is 20 g/L.

In order to facilitate the operation, the branches and leaves of the corn straws are removed before the corn straws are crushed, and the corn straws are crushed by a hammer crusher.

According to an exemplary embodiment of the present invention, a corn stover pretreatment is provided. The corn straw pretreatment substance is obtained by adopting any one of the methods for pretreating corn straws by using sodium phosphate.

After being processed by the pretreatment method, the corn straw has the following characteristics:

the solid recovery rate is between 35 and 65 percent.

The pH value of the pretreated pretreatment liquid is 3-11, the difference of the pH values depends on the concentration of trisodium phosphate, and the pH value after pretreatment is changed from acidity to neutrality to alkalinity along with the increase of the concentration of trisodium phosphate within the scope of the invention.

After the pretreatment, the enzymatic hydrolysis saccharification can be directly carried out, i.e. the single enzyme or the compound enzyme is directly adopted to hydrolyze for 72 hours at 50 ℃ and pH4.8 in acetic acid-sodium acetate buffer solution, thus obtaining various monosaccharides. Wherein the enzyme is cellulase, xylanase and beta-glucosidase or a mixture thereof. FPU is the filter paper enzyme activity unit of cellulase, FXU is the enzyme activity unit of xylanase, and CBU is the enzyme activity unit of beta-glucosidase.

Wherein, FPU, FXU and CBU are respectively:

(1) FPU is the filter paper enzyme activity unit of cellulase, and one FPU unit represents the enzyme amount required by 1 × 6cm (50mg) filter paper as a substrate, and the cellulase can generate 1 μmol glucose within 1min at 50 deg.C and pH 4.8.

(2) FXU is enzyme activity unit of xylanase, and one FXU unit represents that xylanase takes xylan as a substrate

The amount of enzyme required to produce 1. mu. mol xylose in 1min at a temperature of 50 ℃ at pH 4.8.

(3) CBU is the enzyme activity unit of beta-glucosidase, and one CBU unit is the enzyme quantity which takes cellobiose as a substrate and is required by the beta-glucosidase to generate 1 mu mol glucose within 1min at the temperature of 50 ℃ and the pH value of 4.8. Wherein the preferable dosage of the complex enzyme is 10-30 FPU/(g substrate).

The present invention will be further described with reference to the following examples, but the present invention is not limited to the conditions and effects of the examples.

The content of reducing sugars was analyzed using 3, 5-dinitrosalicylic acid (DNS). Reducing sugar yield is reducing sugar concentration x 100%/corn stalk concentration.

Example 1

Taking corn straws with the water content of below 15%, crushing the straws to below 2.8mm by a hammer mill, and carrying out screening to obtain parts between 2.8mm and 0.85mm for pretreatment. Preparing a trisodium phosphate aqueous solution with the concentration of 32.6g/L, putting 50g of corn straw and 500mL of the trisodium phosphate aqueous solution into a small group of pots of a cooking pot, mixing, sealing, putting into the cooking pot, heating to 140 ℃ within 40min, and keeping the temperature at the target temperature for 37 min. And then, deflating, cooling to below 100 ℃ after 40min, opening the cooking pot, taking out the small pot, putting the small pot into a water bath, and cooling to room temperature. The material in the canister was drained and washed to neutrality with water, and the dry weight was measured with a solids recovery of 50.1%. And (3) carrying out enzymolysis saccharification on the pretreated corn straws, wherein the system is 20g/L, solid enzyme is used, the enzyme dosage is 20 FPUg/substrate, and sampling is carried out periodically to determine reducing sugar. The yield of reducing sugar in 72h is 57% (figure 1). The cellulose, hemicellulose and lignin contents of the pretreated corn stalks are 55.0%, 22.5% and 9.4% (table 1).

Example 2

Taking corn straws with the water content of below 15%, crushing the straws to below 2.8mm by a hammer mill, and carrying out screening to obtain parts between 2.8mm and 0.85mm for pretreatment. Preparing a trisodium phosphate aqueous solution with the concentration of 32.6g/L, putting 50g of corn straw and 750mL of the trisodium phosphate aqueous solution into a small group of pots of a cooking pot, mixing, sealing, putting into the cooking pot, heating to 140 ℃ within 40min, and preserving heat for 37min at a target temperature. And then, deflating, cooling to below 100 ℃ after 40min, opening the cooking pot, taking out the small pot, putting the small pot into a water bath, and cooling to room temperature. The material in the canister was drained and washed to neutrality with water, and the dry weight was measured with a solids recovery of 44.5%. And (3) carrying out enzymolysis saccharification on the pretreated corn straws, wherein the system is 20g/L, solid enzyme is used, the enzyme dosage is 20 FPUg/substrate, and sampling is carried out periodically to determine reducing sugar. The yield of reducing sugar in 72h is 65% (figure 1). The cellulose, hemicellulose and lignin contents of the pretreated corn stalks were 63.3%, 27.1%, 3.3% (table 1).

Example 3

Taking corn straws with the water content of below 15%, crushing the straws to below 2.8mm by a hammer mill, and carrying out screening to obtain parts below 0.25mm for pretreatment. Preparing a trisodium phosphate aqueous solution with the concentration of 32.6g/L, putting 50g of corn straw and 500mL of the trisodium phosphate aqueous solution into a small group of pots of a cooking pot, mixing, sealing, putting into the cooking pot, heating to 140 ℃ within 40min, and keeping the temperature at the target temperature for 37 min. And then, deflating, cooling to below 100 ℃ after 40min, opening the cooking pot, taking out the small pot, putting the small pot into a water bath, and cooling to room temperature. The material in the canister was drained and washed to neutrality with water, and the dry weight was measured with a solids recovery of 43.1%. And (3) carrying out enzymolysis saccharification on the pretreated corn straws, wherein the system is 20g/L, solid enzyme is used, the enzyme dosage is 20 FPUg/substrate, and sampling is carried out periodically to determine reducing sugar. The yield of reducing sugar was 61% in 72h (FIG. 1). The cellulose, hemicellulose and lignin contents of the pretreated corn stalks were 56.8%, 26.1% and 5.5% (table 1).

Example 4

Taking corn straws with the water content of below 15%, crushing the straws to below 2.8mm by a hammer mill, and carrying out screening to obtain parts below 0.25mm for pretreatment. Preparing a trisodium phosphate aqueous solution with the concentration of 32.6g/L, putting 50g of corn straw and 750mL of the trisodium phosphate aqueous solution into a small group of pots of a cooking pot, mixing, sealing, putting into the cooking pot, heating to 140 ℃ within 40min, and preserving heat for 37min at a target temperature. And then, deflating, cooling to below 100 ℃ after 40min, opening the cooking pot, taking out the small pot, putting the small pot into a water bath, and cooling to room temperature. The material in the canister was drained and washed to neutrality with water, and the dry weight was measured with a solids recovery of 39.7%. And (3) carrying out enzymolysis saccharification on the pretreated corn straws, wherein the system is 20g/L, solid enzyme is used, the enzyme dosage is 20 FPUg/substrate, and sampling is carried out periodically to determine reducing sugar. The yield of reducing sugar in 72h is 58% (figure 1). The cellulose, hemicellulose and lignin contents of the pretreated corn stalks were 62.0%, 26.6%, 2.0% (table 1).

Example 5

Taking corn straws with the water content of below 15%, crushing the straws to below 2.8mm by a hammer mill, and carrying out screening to obtain parts between 2.8mm and 0.85mm for pretreatment. Preparing a trisodium phosphate aqueous solution with the concentration of 4.3g/L, putting 50g of corn straw and 500mL of the trisodium phosphate aqueous solution into a small group of pots of a cooking pot, mixing, sealing, putting into the cooking pot, heating to 170 ℃ within 40min, and keeping the temperature at the target temperature for 37 min. And then, deflating, cooling to below 100 ℃ after 15min, opening the cooking pot, taking out the small pot, putting the small pot into a water bath, and cooling to room temperature. The contents of the canister were drained and washed to neutrality with water, the dry weight was measured and the solids recovery was calculated to be 64.4%. And (3) carrying out enzymolysis saccharification on the pretreated corn straws, wherein the system is 20g/L, solid enzyme is used, the enzyme dosage is 20 FPUg/substrate, and sampling is carried out periodically to determine reducing sugar. The yield of reducing sugar in 72h was 36.8% (FIG. 2). The cellulose, hemicellulose and lignin contents of the pretreated corn stalks were 56.8%, 26.1% and 6.1% (table 2).

Example 6

Taking corn straws with the water content of below 15%, crushing the straws to below 2.8mm by a hammer mill, and carrying out screening to obtain parts between 2.8mm and 0.85mm for pretreatment. Preparing trisodium phosphate aqueous solution with the concentration of 12.9g/L, putting 50g of corn straw and 500mL of trisodium phosphate aqueous solution into a small group of pots of a cooking pot, mixing, sealing, putting into the cooking pot, heating to 170 ℃ within 40min, and keeping the temperature at the target temperature for 37 min. And then, deflating, cooling to below 100 ℃ after 15min, opening the cooking pot, taking out the small pot, putting the small pot into a water bath, and cooling to room temperature. The material in the canister was drained and washed to neutrality with water, and the dry weight was measured with a solids recovery of 57.3%. And (3) carrying out enzymolysis saccharification on the pretreated corn straws, wherein the system is 20g/L, solid enzyme is used, the enzyme dosage is 20 FPUg/substrate, and sampling is carried out periodically to determine reducing sugar. The yield of reducing sugar in 72h is 50.3% (figure 2). The cellulose, hemicellulose and lignin contents of the pretreated corn stalks were 50.3%, 16.6% and 15.7% (table 2).

Example 7

Taking corn straws with the water content of below 15%, crushing the straws to below 2.8mm by a hammer mill, and carrying out screening to obtain parts between 2.8mm and 0.85mm for pretreatment. Preparing a trisodium phosphate aqueous solution with the concentration of 21.5g/L, putting 50g of corn straw and 500mL of the trisodium phosphate aqueous solution into a small group of pots of a cooking pot, mixing, sealing, putting into the cooking pot, heating to 170 ℃ within 40min, and keeping the temperature at the target temperature for 37 min. And then, deflating, cooling to below 100 ℃ after 15min, opening the cooking pot, taking out the small pot, putting the small pot into a water bath, and cooling to room temperature. The material in the canister was drained and washed to neutrality with water, and the dry weight was measured with a solids recovery of 53.3%. And (3) carrying out enzymolysis saccharification on the pretreated corn straws, wherein the system is 20g/L, solid enzyme is used, the enzyme dosage is 20 FPUg/substrate, and sampling is carried out periodically to determine reducing sugar. The yield of reducing sugar in 72h is 58.7% (figure 2). The cellulose, hemicellulose and lignin contents of the pretreated corn stalks were 51.2%, 19.5%, 12.8% (table 2).

Example 8

Taking corn straws with the water content of below 15%, crushing the straws to below 2.8mm by a hammer mill, and carrying out screening to obtain parts between 2.8mm and 0.85mm for pretreatment. Preparing a trisodium phosphate aqueous solution with the concentration of 30.1g/L, putting 50g of corn straw and 500mL of the trisodium phosphate aqueous solution into a small group of pots of a cooking pot, mixing, sealing, putting into the cooking pot, heating to 170 ℃ within 40min, and keeping the temperature at the target temperature for 37 min. And then, deflating, cooling to below 100 ℃ after 15min, opening the cooking pot, taking out the small pot, putting the small pot into a water bath, and cooling to room temperature. The material in the canister was drained and washed to neutrality with water, and the dry weight was measured with a solids recovery of 50.4%. And (3) carrying out enzymolysis saccharification on the pretreated corn straws, wherein the system is 20g/L, solid enzyme is used, the enzyme dosage is 20 FPUg/substrate, and sampling is carried out periodically to determine reducing sugar. The yield of reducing sugar in 72h is 73.7% (figure 2). The cellulose, hemicellulose and lignin contents of the pretreated corn stalks were 52.3%, 17.7% and 10.2% (table 2).

Example 9

Taking corn straws with the water content of below 15%, crushing the straws to below 2.8mm by a hammer mill, and carrying out screening to obtain parts between 2.8mm and 0.85mm for pretreatment. Preparing a trisodium phosphate aqueous solution with the concentration of 21.5g/L, putting 50g of corn straw and 500mL of the trisodium phosphate aqueous solution into a small group of pots of a cooking pot, mixing, sealing, putting into the cooking pot, heating to 170 ℃ within 40min, and keeping the temperature at the target temperature for 37 min. And then, deflating, cooling to below 100 ℃ after 15min, opening the cooking pot, taking out the small pot, putting the small pot into a water bath, and cooling to room temperature. The material in the canister was drained and washed to neutrality with water, the dry weight was measured and the solids recovery was calculated. And (3) carrying out enzymolysis saccharification on the pretreated corn straws, wherein the system is 20g/L, solid enzyme is used, the enzyme dosage is 20 FPUg/substrate, and sampling is carried out periodically to determine reducing sugar. The yield of reducing sugar in 72h was 81.8% (FIG. 2). The cellulose, hemicellulose and lignin contents of the pretreated corn stalks were 56.9%, 18.9%, 7.5% (table 2).

Comparative example 1

Taking corn straws with the water content of below 15%, crushing the straws to below 2.8mm by a hammer mill, and screening the straws to obtain the part between 2.8mm and 0.85mm for enzymolysis and saccharification. The system is 20g/L, solid enzyme is used, the dosage of the enzyme is 20 FPUg/substrate, and periodic sampling is carried out to determine reducing sugar. The yield of reducing sugar in 72h is 10.7%.

Comparative example 2

Taking corn straws with the water content of below 15%, crushing the straws to below 2.8mm by using a hammer mill, and screening and taking parts between 0.25mm for enzymolysis and saccharification. The system is 20g/L, solid enzyme is used, the dosage of the enzyme is 20 FPUg/substrate, and periodic sampling is carried out to determine reducing sugar. The yield of reducing sugar in 72h is 11.2%.

TABLE 1140 deg.C pretreated corn stover composition

TABLE 2170 ℃ Condition of corn stover composition after pretreatment

From the above description, it can be seen that the above-described embodiments of the present invention achieve the following technical effects: the pretreatment method can realize better pretreatment effect under the condition of lower consumption of trisodium phosphate, and simultaneously, the consumption of trisodium phosphate is reduced, so that the wastewater is easier to treat, and the pretreatment cost is effectively reduced. The method is not only suitable for corn straws, but also can be used for other lignocellulose raw materials under reasonable pretreatment conditions. The industrial production can be realized by utilizing the existing mature equipment and devices. The pretreatment method can reduce the environmental and energy pressure and create economic value.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for pretreating corn stalks, comprising the steps of: mixing the crushed corn straws with a trisodium phosphate solution, and then cooking and carrying out enzymatic saccharification on the obtained mixture.

2. The method of claim 1, wherein the moisture content of the corn stover used for the comminution is controlled to below 15%.

3. The method of claim 1, wherein the corn stalks are ground to less than 2.8 mm.

4. The method of claim 1, wherein the trisodium phosphate solution is an aqueous solution formulated with trisodium phosphate dodecahydrate;

preferably, the concentration of the trisodium phosphate aqueous solution is 4.3 g/L-33.0 g/L.

5. The method as claimed in claim 1, wherein the weight ratio of the trisodium phosphate solution to the corn stalks is 15: 1-10: 1 when the crushed corn stalks are mixed with the aqueous trisodium phosphate solution.

6. The method according to claim 1, wherein the cooking comprises the steps of warming, holding, cooling and washing with water;

preferably, the temperature is raised to 140-180 ℃ within 30-50 min;

preferably, the heat preservation time is 30 min-1 h;

preferably, the temperature is reduced to below 100 ℃ within 20-30 min.

7. The method according to claim 1, wherein the enzyme used for enzymatic saccharification is a cellulase and xylanase complex enzyme;

preferably, the addition amount of the cellulase is 5-30 FPU/g substrate;

preferably, the addition amount of the xylanase is 3-15 FXU/g substrate.

8. The method of claim 1, wherein said corn stover is subjected to branch and leaf removal prior to comminution.

9. The method of claim 1, wherein the corn stover is reduced using a hammer mill.

10. A corn stover pretreatment obtained by treating corn stover with the sodium phosphate pretreatment of any one of claims 1 to 9.