CN111647101A - Method for separating straw components in grades based on hydrothermal-binary catalytic ethanol method - Google Patents
Method for separating straw components in grades based on hydrothermal-binary catalytic ethanol method Download PDFInfo
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Abstract
The invention discloses a method for separating straw components in a grading manner based on a hydrothermal-binary catalytic ethanol method, which comprises the following steps of firstly, carrying out hydrothermal treatment on straws; concentrating the hydrolysate, and precipitating with ethanol to obtain an ethanol precipitation solid-phase product and filtrate A; drying the alcohol precipitation solid phase product to obtain hemicellulose; preparing a reaction solution by using the filtrate A; mixing the hydrothermal solid-phase product with the reaction solution, and performing binary catalytic ethanol method treatment to obtain a binary catalytic ethanol method solid-phase product and a filtrate B; diluting and precipitating the filtrate B, and filtering to obtain lignin and filtrate C; drying the binary catalytic ethanol method solid phase product to obtain crude cellulose; according to the invention, a hydrothermal method is adopted to remove hemicellulose in the straws, then a binary catalytic ethanol method is adopted to remove lignin, and then the filtrate obtained by the binary catalytic ethanol method is diluted and precipitated to extract lignin, so that the hemicellulose, the lignin and the crude cellulose in the straws are separated and extracted in a grading manner; the separation and extraction process is simple, and the extraction rate of straw components is high.
Description
Technical Field
The invention belongs to the technical field of lignocellulose biomass refining, and particularly relates to a method for separating straw components in a grading manner based on a hydrothermal-binary catalytic ethanol method.
Background
Lignocellulosic biomass resources on earth are very abundant, with up to 2000 million tons of resources being producible annually by photosynthesis, but human beings utilize only 3.5% of their total; among them, the separation of cellulose, hemicellulose and lignin is one of the major technical bottlenecks that restrict the large-scale utilization of lignocellulosic biomass resources. Traditional acid method, alkaline process and organic solvent separate the bionass component and all have certain drawback, have greater pollution to the environment on the one hand, on the other hand is to the separation of single component mostly, separate and get the cellulose mostly, and hemicellulose and lignin removed are not separated effectively, still exist in the waste liquid in the mixed state, are difficult to the high value to utilize. Even if lignin and hemicellulose in the waste liquid are separated and extracted subsequently, the separation process is complex, the effect is poor and the cost is high.
Disclosure of Invention
Aiming at the technical problems in the prior art, the invention provides a method for separating straw components by stages based on a hydrothermal-binary catalytic ethanol method, which aims to solve the problem that the conventional separation method cannot realize the separation of three major components of cellulose, hemicellulose and lignin in the straws under the cleaner process condition.
In order to achieve the purpose, the invention adopts the technical scheme that:
the invention provides a method for separating straw components in a graded manner based on a hydrothermal-binary catalytic ethanol method, which comprises the following steps:
step 1, carrying out hydrothermal treatment on straws, and filtering to obtain a hydrothermal solid-phase product and a hydrolysate;
step 2, concentrating the hydrolysate obtained in the step 1, precipitating with ethanol, and filtering to obtain an ethanol precipitation solid-phase product and a filtrate A;
step 4, adding water, hydrogen peroxide and sodium hydroxide into the filtrate A to prepare a reaction solution;
step 5, mixing the hydrothermal method solid-phase product with the reaction solution in the step 4, and performing binary catalytic ethanol method treatment to obtain a binary catalytic ethanol method solid-phase product and a filtrate B;
step 6, diluting and precipitating the filtrate B in the step 5, filtering and drying to obtain lignin and filtrate C;
and 7, drying the binary catalytic ethanol method solid-phase product in the step 5 to obtain the crude cellulose.
Further, in the step 1, the straw is one of wheat straw, corn straw, rice straw, bagasse and cotton straw.
Further, in the step 1, when the straw is subjected to hydrothermal treatment, the straw and water are mixed according to the solid-liquid ratio of (1:10) - (1:32) g/mL, and the hydrothermal treatment is carried out for 10-150min at the temperature of 130-.
Further, in the step 2, the concentration ratio is 5-85%; the alcohol precipitation process adopts 80-100% ethanol to precipitate the concentrated solution, and the alcohol precipitation ratio is (1:2) - (1: 6).
Further, in the step 3, the alcohol precipitation solid phase product is dried by blowing air at the constant temperature of 80-110 ℃.
Further, in the step 4, the mass fraction of the ethanol in the reaction solution is 40-80%; the mass of the added hydrogen peroxide is 0.1-5% of the oven-dried mass of the solid-phase product of the hydrothermal method, and the mass of the added sodium hydroxide is 0.1-5% of the oven-dried mass of the solid-phase product of the hydrothermal method.
Further, in step 5, the solid-to-liquid ratio of the hydrothermal solid-phase product to the reaction solution is (1:10) - (1:24) g/mL, and the conditions of the binary catalytic ethanol method are as follows: the temperature is 160-210 ℃, the rotating speed is 200-650rpm, and the heat preservation time is 15-180 min.
Further, in the step 6, in the dilution and precipitation process, the filtrate B is diluted by deionized water, the pH is adjusted to 2-6, and the filtrate B is kept stand to precipitate solid phase components in the filtrate B; wherein the dilution volume ratio is (1:2) - (1: 5); the drying process adopts air blast drying, and the drying temperature is 105-120 ℃.
Further, step 6 includes recovering ethanol from the filtrate C by a distillation process.
Further, in step 7, the solid phase product of the binary catalytic ethanol method is dried by blowing air at constant temperature under the condition of 105-120 ℃.
Compared with the prior art, the invention has the beneficial effects that:
the invention provides a method for separating straw components in a grading manner based on a hydrothermal-binary catalytic ethanol method, which is characterized in that hemicellulose in straws is removed by adopting a hydrothermal method, and the hemicellulose is extracted by alcohol precipitation; then removing lignin by adopting a binary catalytic ethanol method, diluting and precipitating a solid-phase product in the filtrate of the binary catalytic ethanol method, extracting lignin, and drying the solid-phase product of the binary catalytic ethanol method to obtain cellulose; the method realizes the fractional separation and extraction of hemicellulose, lignin and cellulose in the straws, and well retains the cellulose; extracting lignin by using a binary catalytic ethanol method, and recycling ethanol in alcohol precipitation and the binary catalytic ethanol method; the separation and extraction process is simple, the extraction rate of the straw components is high, the biological structure deconstruction of the lignocellulose biomass and the separation and extraction of the three components are realized by a low-pollution process, and the method has positive significance for the high-valued utilization of biomass resources.
Furthermore, the ethanol in the filtrate C is recovered by adopting a distillation process, the recovered ethanol can be used in an ethanol precipitation process, and the ethanol precipitated filtrate A is used for processing by a binary catalytic ethanol method, so that the cyclic utilization of an ethanol solvent is realized, and the separation cost is effectively reduced.
According to the method for fractionating straw components based on the hydrothermal-binary catalytic ethanol method, hemicellulose is preferentially removed by adopting the hydrothermal method, lignin is extracted on the basis of preferentially extracting the hemicellulose, and finally coarse cellulose is remained, so that fractional extraction of three major components can be realized, high-value utilization of lignocellulose biomass resources is promoted, and meanwhile, the cost is reduced; the extraction rate of hemicellulose in the straw components reaches 30.1-45.0%, the extraction rate of lignin is 35.5-80.6%, and the extraction rate of cellulose is 70.5-93.1%.
The lignocellulose biomass raw materials such as the straws and the like are mainly formed by mixing three major components of hemicellulose, lignin and cellulose with different physical and chemical properties, and form a special natural degradation-resistant structure of the raw materials together; the separation and extraction are difficult to be simultaneously carried out in the same treatment process, and the gradual deconstruction and separation are needed in different physical and chemical processes and under harsher conditions; the fractionation method of the invention firstly adopts hydrothermal treatment to preferentially remove hemicellulose, and the hemicellulose is precipitated and extracted by high-concentration ethanol solution; then the lignin is treated and separated by adopting the binary catalytic ethanol, and is diluted, precipitated and extracted, and the residual solid phase product is crude cellulose, so that the three major components are extracted in a grading way; the method can meet the requirements of separating hemicellulose firstly, then separating lignin and finally remaining cellulose, realizes the separation and extraction of the three components and provides necessary preconditions for the subsequent high-value utilization of the three components; in the invention, the binary catalyst formed by sodium hydroxide and hydrogen peroxide can obviously enhance the degradation effect of the ethanol method on lignin through synergistic action, so that the lignin is dissolved in the ethanol solution in small molecules, thereby obviously enhancing the delignification effect; meanwhile, the hydrothermal-ethanol method formed by combining the hydrothermal method and the ethanol method can realize the fractionation of the three major components by utilizing the separation advantages of hemicellulose and lignin respectively.
Drawings
FIG. 1 is a bar graph of the extraction rates of hemicellulose, lignin and cellulose obtained by fractionation of wheat straw in example 1;
FIG. 2 is a stacking diagram of the analysis of conservation of substances after fractionation of wheat straw in example 1.
Detailed Description
In order to make the technical problems, technical solutions and advantageous effects of the present invention more apparent, the following embodiments further describe the present invention in detail. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
The invention provides a method for separating straw components in a graded manner based on a hydrothermal-binary catalytic ethanol method, which comprises the following steps:
step 1, mixing straws and water according to the solid-to-liquid ratio of (1:10) - (1:32) g/mL, carrying out hydrothermal treatment for 10-150min at the temperature of 130-200 ℃, removing hemicellulose, and filtering to obtain a hydrothermal solid-phase product and a hydrolysate; wherein the straw is one of wheat straw, corn straw, rice straw, bagasse and cotton straw.
Step 2, concentrating the hydrolysate obtained in the step 1 according to a concentration ratio of 5-85% to obtain a concentrated solution; precipitating the concentrated solution with 80-100% ethanol, and filtering to obtain a solid-phase product precipitated with ethanol and a filtrate A; wherein the alcohol precipitation ratio is (1:2) - (1: 6); the alcohol precipitation process adopts ethanol to dilute the concentrated solution, so as to reduce the solubility of solid phase components of the concentrated solution, and separate out the solid phase components in a precipitation form.
step 4, adding deionized water, hydrogen peroxide and sodium hydroxide into the filtrate A, and uniformly mixing to obtain a reaction solution; ethanol is mainly used in the reaction solution, wherein the mass fraction of the ethanol is 40-80%; the mass of the added hydrogen peroxide is 0.1-5% of the oven-dried mass of the solid-phase product of the hydrothermal method, and the mass of the added sodium hydroxide is 0.1-5% of the oven-dried mass of the solid-phase product of the hydrothermal method.
And 5, mixing the hydrothermal solid-phase product in the step 1 with the reaction solution in the step 4 according to the solid-liquid ratio of (1:10) - (1:24) g/mL, treating by a binary catalytic ethanol method to remove lignin under the conditions of the temperature of 160-210 ℃, the rotation speed of 200-650rpm and the heat preservation time of 15-180min, and filtering to obtain a binary catalytic ethanol method solid-phase product and a filtrate B.
Step 6, diluting the filtrate B in the step 5 by deionized water in a dilution volume ratio of (1:2) - (1:5) to obtain a diluted solution; regulating the pH value of the diluted solution to 2-6 by adopting formic acid, standing to precipitate solid phase components in the filtrate B, filtering, and drying to obtain lignin and filtrate C; wherein, the drying process adopts forced air drying, and the drying temperature is 105-120 ℃; and (3) recovering the ethanol in the filtrate C by adopting a distillation process, wherein the recovered ethanol can be used for the ethanol precipitation process in the step 2, and the ethanol precipitated filtrate A in the step 2 is used for the treatment by a binary catalytic ethanol method, so that the cyclic utilization of an ethanol solvent is realized.
And 7, carrying out forced air constant-temperature drying on the binary catalytic ethanol method solid-phase product in the step 5 at the temperature of 105-120 ℃ to obtain the crude cellulose.
According to the method for separating the straw components in a grading manner based on the hydrothermal-binary catalytic ethanol method, hemicellulose in the straw components is removed by the hydrothermal method, the hemicellulose removed from hydrolysate is diluted and precipitated by an ethanol solvent and extracted, then lignin is removed by the binary catalytic ethanol method, lignin in filtrate obtained by the binary catalytic ethanol method is diluted and precipitated by deionized water and extracted, and finally crude cellulose is obtained in the rest, so that the three components of the straw are extracted in a grading manner, the solvent is recycled, the problems of complex separation process, high cost and the like of a traditional hemicellulose and lignin mixed system can be solved, and the method has important significance for solving the problems of resource waste, environmental pollution and high-value utilization of biomass.
Example 1
In example 1, when wheat straw components are fractionated by a hydrothermal-binary catalytic ethanol method, the method comprises the following steps:
step 1, mixing wheat straws and water according to a solid-to-liquid ratio of 1:24g/mL, carrying out hydrothermal treatment for 40min at the temperature of 180 ℃ to remove hemicellulose, and filtering to obtain a hydrothermal solid-phase product and hydrolysate.
Step 2, concentrating the hydrolysate obtained in the step 1 according to a concentration ratio of 80% to obtain a concentrated solution; precipitating the concentrated solution with 90% ethanol, and filtering to obtain an ethanol precipitation solid-phase product and filtrate A; wherein the alcohol precipitation ratio is 1: 4.
step 4, adding deionized water, hydrogen peroxide and sodium hydroxide into the filtrate A, and uniformly mixing to obtain a reaction solution; ethanol is mainly used in the reaction solution, wherein the mass fraction of the ethanol is 50%; the mass of the added hydrogen peroxide is 3% of the oven-dried mass of the solid-phase product of the hydrothermal method, and the mass of the added sodium hydroxide is 3% of the oven-dried mass of the solid-phase product of the hydrothermal method.
And 5, mixing the hydrothermal solid-phase product in the step 1 with the reaction solution in the step 4 according to the solid-liquid ratio of 1:16g/mL, performing binary catalytic ethanol method treatment to remove lignin under the conditions of 190 ℃ of temperature, 350rpm of rotation speed and 90min of heat preservation time, and filtering to obtain a binary catalytic ethanol method solid-phase product and a filtrate B.
Step 6, diluting the filtrate B in the step 5 by deionized water in a dilution volume ratio of 1:3 to obtain a diluted solution; regulating the pH value of the diluted solution to 3 by adopting formic acid, standing to precipitate solid phase components in the filtrate B, filtering, and drying to obtain lignin and filtrate C; wherein, the drying process adopts forced air drying, and the drying temperature is 105 ℃; and (3) recovering the ethanol in the filtrate C by adopting a distillation process, wherein the recovered ethanol can be used for the alcohol precipitation process in the step 2.
And 7, blowing the binary catalytic ethanol method solid-phase product in the step 5 at constant temperature and drying at 105 ℃ to obtain the crude cellulose.
As shown in the attached figure 1, the detection results show that the attached figure 1 shows a bar graph of the extraction rates of cellulose, hemicellulose and lignin obtained by the step separation of wheat straws by using a hydrothermal-binary catalytic ethanol method in the embodiment 1, and the extraction rate of the hemicellulose is 38.1%; the extraction rate of lignin is 62.7 percent, the extraction rate of cellulose is 86.1 percent, the three major components of the wheat straw can be extracted in a grading way, and the extraction rate is higher.
As shown in the attached figure 2, the attached figure 2 shows a substance conservation analysis stacking chart of the wheat straw subjected to fractionation by the hydrothermal-binary catalytic ethanol method in the example 1, and the losses of hemicellulose, lignin and cellulose are respectively 24.7%, 22.8% and 13.9% as can be seen from the attached figure 2; the hydrothermal-binary catalytic ethanol method has less degradation to the three major components of hemicellulose, lignin and cellulose, and has lower loss content.
Example 2
In example 2, the step of fractionating corn stalk fractions by hydrothermal-binary catalytic ethanol method comprises the following steps:
step 1, mixing corn straws and water according to a solid-to-liquid ratio of 1:10g/mL, carrying out hydrothermal treatment for 10min at a temperature of 130 ℃ to remove hemicellulose, and filtering to obtain a hydrothermal solid-phase product and hydrolysate.
Step 2, concentrating the hydrolysate obtained in the step 1 according to a concentration ratio of 85% to obtain a concentrated solution; precipitating the concentrated solution with 80% ethanol, and filtering to obtain an ethanol precipitation solid phase product and filtrate A; wherein the alcohol precipitation ratio is 1: 6.
step 4, adding deionized water, hydrogen peroxide and sodium hydroxide into the filtrate A, and uniformly mixing to obtain a reaction solution; ethanol is mainly used in the reaction solution, wherein the mass fraction of the ethanol is 40%; the mass of the added hydrogen peroxide is 0.1 percent of the oven-dried mass of the solid-phase product of the hydrothermal method, and the mass of the added sodium hydroxide is 0.1 percent of the oven-dried mass of the solid-phase product of the hydrothermal method.
And 5, mixing the hydrothermal solid-phase product in the step 1 with the reaction solution in the step 4 according to the solid-liquid ratio of 1:10g/mL, performing binary catalytic ethanol method treatment to remove lignin at the temperature of 160 ℃, the rotation speed of 200rpm and the heat preservation time of 15min, and filtering to obtain a binary catalytic ethanol method solid-phase product and a filtrate B.
Step 6, diluting the filtrate B in the step 5 by using deionized water, wherein the dilution volume ratio is 1:2, so as to obtain a diluted solution; regulating the pH value of the diluted solution to 2 by adopting formic acid, standing to precipitate solid phase components in the filtrate B, filtering, and drying to obtain lignin and filtrate C; wherein, the drying process adopts forced air drying, and the drying temperature is 110 ℃; and (3) recovering the ethanol in the filtrate C by adopting a distillation process, wherein the recovered ethanol can be used for the alcohol precipitation process in the step 2.
And 7, blowing the binary catalytic ethanol method solid-phase product in the step 5 at constant temperature for drying at 110 ℃ to obtain the crude cellulose.
The detection result shows that the extraction rate of hemicellulose after the corn straw is graded and separated by using a hydrothermal-binary catalytic ethanol method in the embodiment 2 is 34.1 percent; the extraction rate of lignin was 35.5%, and the extraction rate of cellulose was 93.1%.
Example 3
In example 3, the step of fractionating the straw fraction of rice by hydrothermal-binary catalytic ethanol method comprises the following steps:
step 1, mixing rice straws and water according to a solid-liquid ratio of 1:16g/mL, carrying out hydrothermal treatment for 90min at the temperature of 150 ℃ to remove hemicellulose, and filtering to obtain a hydrothermal solid-phase product and hydrolysate.
Step 2, concentrating the hydrolysate obtained in the step 1 according to a concentration ratio of 60% to obtain a concentrated solution; precipitating the concentrated solution with 95% ethanol, and filtering to obtain an ethanol precipitation solid-phase product and a filtrate A; wherein the alcohol precipitation ratio is 1: 6.
step 4, adding deionized water, hydrogen peroxide and sodium hydroxide into the filtrate A, and uniformly mixing to obtain a reaction solution; ethanol is mainly used in the reaction solution, wherein the mass fraction of the ethanol is 65%; the mass of the added hydrogen peroxide is 1% of the oven-dried mass of the solid-phase product of the hydrothermal method, and the mass of the added sodium hydroxide is 1% of the oven-dried mass of the solid-phase product of the hydrothermal method.
And 5, mixing the hydrothermal solid-phase product in the step 1 with the reaction solution in the step 4 according to the solid-liquid ratio of 1:20g/mL, performing binary catalytic ethanol method treatment to remove lignin under the conditions of 200 ℃ of temperature, 400rpm of rotation speed and 150min of heat preservation time, and filtering to obtain a binary catalytic ethanol method solid-phase product and a filtrate B.
Step 6, diluting the filtrate B in the step 5 by deionized water in a dilution volume ratio of 1:3 to obtain a diluted solution; regulating the pH value of the diluted solution to 6 by adopting formic acid, standing to precipitate solid phase components in the filtrate B, filtering, and drying to obtain lignin and filtrate C; wherein, the drying process adopts forced air drying, and the drying temperature is 115 ℃; and (3) recovering the ethanol in the filtrate C by adopting a distillation process, wherein the recovered ethanol can be used for the alcohol precipitation process in the step 2.
And 7, blowing and drying the binary catalytic ethanol method solid-phase product in the step 5 at constant temperature at 115 ℃ to obtain the crude cellulose.
The detection result shows that the extraction rate of hemicellulose after the rice straw is subjected to fractionation by using a hydrothermal-binary catalytic ethanol method in example 3 is 45.0%; the extraction rate of lignin was 71.1%, and the extraction rate of cellulose was 79.3%.
Example 4
In example 4, the step of fractionating cotton straw components by hydrothermal-binary catalytic ethanol method comprises the following steps:
step 1, mixing cotton straws and water according to a solid-to-liquid ratio of 1:32g/mL, carrying out hydrothermal treatment for 150min at the temperature of 200 ℃ to remove hemicellulose, and filtering to obtain a hydrothermal solid-phase product and hydrolysate.
Step 2, concentrating the hydrolysate obtained in the step 1 according to a concentration ratio of 5% to obtain a concentrated solution; precipitating the concentrated solution with 100% ethanol, and filtering to obtain an ethanol precipitation solid-phase product and filtrate A; wherein the alcohol precipitation ratio is 1: 2.
step 4, adding deionized water, hydrogen peroxide and sodium hydroxide into the filtrate A, and uniformly mixing to obtain a reaction solution; ethanol is mainly used in the reaction solution, wherein the mass fraction of the ethanol is 80%; the mass of the added hydrogen peroxide is 5% of the oven-dried mass of the solid-phase product of the hydrothermal method, and the mass of the added sodium hydroxide is 5% of the oven-dried mass of the solid-phase product of the hydrothermal method.
And 5, mixing the hydrothermal solid-phase product in the step 1 with the reaction solution in the step 4 according to the solid-liquid ratio of 1:20g/mL, performing binary catalytic ethanol method treatment to remove lignin under the conditions of the temperature of 210 ℃, the rotating speed of 650rpm and the heat preservation time of 180min, and filtering to obtain a binary catalytic ethanol method solid-phase product and a filtrate B.
Step 6, diluting the filtrate B in the step 5 by using deionized water, wherein the dilution volume ratio is 1:5, so as to obtain a diluted solution; regulating the pH value of the diluted solution to 2 by adopting formic acid, standing to precipitate solid phase components in the filtrate B, filtering, and drying to obtain lignin and filtrate C; wherein, the drying process adopts forced air drying, and the drying temperature is 120 ℃; and (3) recovering the ethanol in the filtrate C by adopting a distillation process, wherein the recovered ethanol can be used for the alcohol precipitation process in the step 2.
And 7, blowing and drying the binary catalytic ethanol method solid-phase product in the step 5 at constant temperature at 120 ℃ to obtain the crude cellulose.
The detection result shows that in the embodiment 4, after the rice straws are subjected to fractionation by using a hydrothermal-binary catalytic ethanol method, the extraction rate of hemicellulose is 30.1%; the extraction rate of lignin is 80.6%, and the extraction rate of cellulose is 70.5%.
Example 5
In example 5, the step of fractionating bagasse components by hydrothermal-binary catalytic ethanol method comprises the following steps:
step 1, mixing bagasse and water according to a solid-to-liquid ratio of 1:20g/mL, carrying out hydrothermal treatment at 180 ℃ for 60min to remove hemicellulose, and filtering to obtain a hydrothermal solid-phase product and a hydrolysate.
Step 2, concentrating the hydrolysate obtained in the step 1 according to a concentration ratio of 60% to obtain a concentrated solution; precipitating the concentrated solution with 85% ethanol, and filtering to obtain an ethanol precipitation solid-phase product and filtrate A; wherein the alcohol precipitation ratio is 1: 4.
step 4, adding deionized water, hydrogen peroxide and sodium hydroxide into the filtrate A, and uniformly mixing to obtain a reaction solution; ethanol is mainly used in the reaction solution, wherein the mass fraction of the ethanol is 65%; the mass of the added hydrogen peroxide is 5% of the oven-dried mass of the solid-phase product of the hydrothermal method, and the mass of the added sodium hydroxide is 5% of the oven-dried mass of the solid-phase product of the hydrothermal method.
And 5, mixing the hydrothermal solid-phase product in the step 1 with the reaction solution in the step 4 according to the solid-liquid ratio of 1:20g/mL, performing binary catalytic ethanol method treatment to remove lignin under the conditions of 180 ℃ of temperature, 450rpm of rotation speed and 30min of heat preservation time, and filtering to obtain a binary catalytic ethanol method solid-phase product and a filtrate B.
Step 6, diluting the filtrate B in the step 5 by deionized water in a dilution volume ratio of 1:3 to obtain a diluted solution; regulating the pH value of the diluted solution to 3 by adopting formic acid, standing to precipitate solid phase components in the filtrate B, filtering, and drying to obtain lignin and filtrate C; wherein, the drying process adopts forced air drying, and the drying temperature is 115 ℃; and (3) recovering the ethanol in the filtrate C by adopting a distillation process, wherein the recovered ethanol can be used for the alcohol precipitation process in the step 2.
And 7, blowing and drying the binary catalytic ethanol method solid-phase product in the step 5 at constant temperature at 115 ℃ to obtain the crude cellulose.
The detection result shows that in the embodiment 5, after bagasse is subjected to fractionation by using a hydrothermal-binary catalytic ethanol method, the extraction rate of hemicellulose is 35.2%; the extraction rate of lignin is 52.6%, and the extraction rate of cellulose is 85.9%.
Aiming at the problem that the existing hemicellulose and lignin are difficult to extract from a mixed system in a grading manner by a hydrothermal-binary catalytic ethanol method, the hemicellulose is extracted by adding ethanol solvent into hydrolysate after straw treatment by the hydrothermal method to dilute and precipitate, and then the lignin is extracted by adding deionized water into filtrate after a hydrothermal solid-phase product is treated by the binary catalytic ethanol method to dilute and precipitate, so that the grading extraction of the hemicellulose and the lignin is realized, the cellulose is well reserved, and the solvent is recycled; the extraction rate of hemicellulose in the straw components by the fractional extraction method reaches 30.1-45.0%, the extraction rate of lignin is 35.5-80.6%, and the extraction rate of cellulose is 70.5-93.1%.
The above-described embodiment is only one of the embodiments that can implement the technical solution of the present invention, and the scope of the present invention is not limited by the embodiment, but includes any variations, substitutions and other embodiments that can be easily conceived by those skilled in the art within the technical scope of the present invention disclosed.
Claims (10)
1. A method for separating straw components in a grading manner based on a hydrothermal-binary catalytic ethanol method is characterized by comprising the following steps:
step 1, carrying out hydrothermal treatment on straws, and filtering to obtain a hydrothermal solid-phase product and a hydrolysate;
step 2, concentrating the hydrolysate obtained in the step 1, precipitating with ethanol, and filtering to obtain an ethanol precipitation solid-phase product and a filtrate A;
step 3, drying the alcohol precipitation solid phase product to obtain hemicellulose;
step 4, adding water, hydrogen peroxide and sodium hydroxide into the filtrate A to prepare a reaction solution;
step 5, mixing the hydrothermal method solid-phase product with the reaction solution in the step 4, and performing binary catalytic ethanol method treatment to obtain a binary catalytic ethanol method solid-phase product and a filtrate B;
step 6, diluting and precipitating the filtrate B in the step 5, filtering and drying to obtain lignin and filtrate C;
and 7, drying the binary catalytic ethanol method solid-phase product in the step 5 to obtain the crude cellulose.
2. The method for fractionating straw components based on the hydrothermal-binary catalytic ethanol method according to claim 1, wherein in step 1, the straw is one of wheat straw, corn straw, rice straw, bagasse and cotton straw.
3. The method for fractional separation of straw components based on hydrothermal-binary catalytic ethanol method as claimed in claim 1, wherein in step 1, when the straw is subjected to hydrothermal treatment, the straw and water are mixed according to the solid-to-liquid ratio of (1:10) - (1:32) g/mL, and the hydrothermal treatment is carried out for 10-150min at the temperature of 130-200 ℃.
4. The method for fractionating straw components based on the hydrothermal-binary catalytic ethanol method as claimed in claim 1, wherein in the step 2, the concentration ratio is 5% to 85%; the alcohol precipitation process adopts 80-100% ethanol to precipitate the concentrated solution, and the alcohol precipitation ratio is (1:2) - (1: 6).
5. The method for separating straw components by stages based on the hydrothermal-binary catalytic ethanol method as claimed in claim 1, wherein in the step 3, the alcohol precipitation solid phase product is dried by blowing air at a constant temperature of 80-110 ℃.
6. The method for fractionating straw components based on the hydrothermal-binary catalytic ethanol method according to claim 1, wherein in step 4, the mass fraction of ethanol in the reaction solution is 40% -80%; the mass of the added hydrogen peroxide is 0.1-5% of the oven-dried mass of the solid-phase product of the hydrothermal method, and the mass of the added sodium hydroxide is 0.1-5% of the oven-dried mass of the solid-phase product of the hydrothermal method.
7. The method for fractionating straw components based on the hydrothermal-binary catalytic ethanol method as claimed in claim 1, wherein in step 5, the solid-to-liquid ratio of the hydrothermal solid-phase product to the reaction solution is (1:10) - (1:24) g/mL, and the conditions of the binary catalytic ethanol method treatment are as follows: the temperature is 160-210 ℃, the rotating speed is 200-650rpm, and the heat preservation time is 15-180 min.
8. The method for fractionating straw components based on the hydrothermal-binary catalytic ethanol method according to claim 1, wherein in the step 6, in the dilution and precipitation process, the filtrate B is diluted by deionized water, the pH is adjusted to 2-6, and the filtrate B is left to stand to precipitate solid-phase components in the filtrate B; wherein the dilution volume ratio is (1:2) - (1: 5); the drying process adopts air blast drying, and the drying temperature is 105-120 ℃.
9. The method for fractionating straw components based on the hydrothermal-binary catalytic ethanol method as claimed in claim 1, wherein step 6 further comprises recovering ethanol from the filtrate C by distillation.
10. The method for separating straw components by stages based on hydrothermal-binary catalytic ethanol method as claimed in claim 1, wherein in step 7, the solid phase product of the binary catalytic ethanol method is dried by blowing air at constant temperature under the conditions of 105-120 ℃.
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| CN115536861A (en) * | 2022-08-25 | 2022-12-30 | 华南农业大学 | Pretreatment method for full-component utilization of corn straws and application thereof |
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