阅读说明：本技术 一种从农林生物质原料中提纯木质素的方法 (Method for purifying lignin from agriculture and forestry biomass raw materials ) 是由 孙付保 曾诚 宋国杰 任洪艳 孟超然 于 2020-06-24 设计创作，主要内容包括：本发明公开了一种从农林生物质原料中提纯木质素的方法,从农林生物质原料中提纯木质素的方法包括如下步骤：将农林生物质原料、甘油混合得到混合液,在碱催化条件下蒸煮得到蒸煮液,其中,所述农林生物质原料和所述甘油的质量比为(1:5)-(1:15)；对所述蒸煮液降温,过滤处理得到富含纤维素的基质和第一过滤液；将所述基质与低沸点有机溶剂混合洗涤,过滤处理得到第二过滤液；再将所述第一过滤液和第二过滤液混合得到合并液,之后采用微滤膜对所述合并液微滤得到微滤液；采用超滤膜对所述微滤液进行超滤得到截留液和超滤液,调节所述截留液的pH至2.0-3.0得到含木质素的产物。上述方法具有节能环保、成本低廉且木质素的提纯度高的优点。(The invention discloses a method for purifying lignin from an agricultural and forestry biomass raw material, which comprises the following steps: mixing an agricultural and forestry biomass raw material and glycerol to obtain a mixed solution, and cooking under an alkali catalysis condition to obtain a cooking solution, wherein the mass ratio of the agricultural and forestry biomass raw material to the glycerol is (1:5) - (1: 15); cooling the cooking liquor, and filtering to obtain a cellulose-rich matrix and a first filtrate; mixing and washing the substrate and a low-boiling-point organic solvent, and filtering to obtain a second filtrate; mixing the first filtrate and the second filtrate to obtain a combined solution, and then carrying out microfiltration on the combined solution by adopting a microfiltration membrane to obtain a microfiltration solution; and (3) carrying out ultrafiltration on the micro-filtrate by adopting an ultrafiltration membrane to obtain trapped fluid and ultrafiltrate, and adjusting the pH of the trapped fluid to 2.0-3.0 to obtain a product containing lignin. The method has the advantages of energy conservation, environmental protection, low cost and high lignin purification degree.)

1. A method for purifying lignin from an agricultural and forestry biomass raw material is characterized by comprising the following steps:

(1) mixing an agricultural and forestry biomass raw material and glycerol to obtain a mixed solution, and cooking under an alkali catalysis condition to obtain a cooking solution, wherein the mass ratio of the agricultural and forestry biomass raw material to the glycerol is (1:5) - (1: 15);

(2) cooling the cooking liquor, and filtering to obtain a cellulose-rich matrix and a first filtrate;

mixing and washing the substrate and a low-boiling-point organic solvent, and filtering to obtain a second filtrate;

mixing the first filtrate and the second filtrate to obtain a combined solution, and then carrying out microfiltration on the combined solution by adopting a microfiltration membrane to obtain a microfiltration solution;

(3) and (3) carrying out ultrafiltration on the micro-filtrate by adopting an ultrafiltration membrane to obtain trapped fluid and ultrafiltrate, and adjusting the pH of the trapped fluid to 2.0-3.0 to obtain a product containing lignin.

2. The method for purifying lignin from an agricultural and forestry biomass feedstock according to claim 1, wherein after step (3), further comprising distilling the ultrafiltrate to obtain ethanol and glycerol.

3. The method of purifying lignin from an agricultural or forestry biomass feedstock as claimed in claim 1, wherein the low boiling point organic solvent is selected from at least one of methanol, ethanol, formic acid, acetic acid, acetone, ethyl formate and ethyl acetate.

4. The method of claim 1, wherein the mass to volume ratio of the substrate to the low boiling point organic solvent is from (1:5) to (1: 20).

5. The method for purifying lignin from an agricultural and forestry biomass material as claimed in any one of claims 1 to 4, wherein the cooking treatment temperature is 150 ℃ and 240 ℃, and the cooking treatment time is 15-120 min.

6. The method for purifying lignin from an agricultural and forestry biomass material according to any one of claims 1 to 4, wherein the pressure of the ultrafiltration is 0.05-0.3MP and the temperature of the ultrafiltration is 25-80 ℃.

7. The method for purifying lignin from an agricultural and forestry biomass material according to any one of claims 1 to 4, wherein the ultrafiltration membrane is made of a material selected from PL-based cellulose membranes.

8. The method for purifying lignin from an agricultural and forestry biomass material as claimed in any one of claims 1 to 4, wherein the pore size of the microfiltration membrane is 0.4 to 70 μm.

9. The method for purifying lignin from an agricultural and forestry biomass material as claimed in any one of claims 1 to 4, wherein the ultrafiltration membrane has a molecular weight cut-off of 500-7000 Da.

Technical Field

The invention relates to the technical field of resource utilization of agriculture and forestry biomass raw materials and biomass chemical industry, in particular to a method for purifying lignin from agriculture and forestry biomass raw materials.

Background

Environmental challenges and energy safety have led society to urgently seek sustainable renewable carbon neutral resources as raw materials for the production of biobased materials, chemicals and bioenergy. Among them, biorefinery of biomass feedstocks with organic solvents has a number of unique advantages, such as: the applicability to various cellulosic raw materials is strong; the consumption of water, electricity and chemicals is less; low economic cost, etc., and thus is widely concerned by researchers at home and abroad.

However, the traditional treatment method of the agriculture and forestry biomass raw material not only wastes energy but also destroys the environment in the process of extracting lignin, and can not effectively extract the lignin in the agriculture and forestry biomass raw material. Particularly, on the one hand, the traditional treatment method can cause that the treated waste liquid still contains a lot of unconsumed glycerin; on the other hand, the lignin separation effect is poor, a large amount of removed lignin is dissolved in waste liquid to form black liquor, and the black liquor is discharged together with the unconsumed glycerol, so that the purification degree of the lignin is low, and the lignin is wasted. Therefore, the purification of lignin in cellulosic agricultural and forestry biomass raw materials is a problem to be solved urgently.

Researchers have proposed to extract lignin from cellulosic agricultural and forestry biomass raw materials by adding water and acid, but the method has obvious disadvantages, namely: a large amount of water resources are consumed; second, water has a higher boiling point than other low boiling point organic solvents and is difficult to evaporate, thereby requiring a large amount of electric power. Thirdly, when the pH value of the solution is reduced by adding acid, a large amount of acid (such as hydrochloric acid, sulfuric acid and the like) needs to be added, and the cost is high.

Disclosure of Invention

The invention aims to provide a method for effectively purifying lignin from an agricultural and forestry biomass raw material, and the method has the advantages of energy conservation, environmental protection, low cost and high lignin purification degree.

In order to solve the technical problems, the invention provides a method for purifying lignin from an agricultural and forestry biomass raw material, which comprises the following steps:

a method for purifying lignin from an agricultural and forestry biomass raw material comprises the following steps:

(1) mixing an agricultural and forestry biomass raw material and glycerol to obtain a mixed solution, and cooking under an alkali catalysis condition to obtain a cooking solution, wherein the mass ratio of the agricultural and forestry biomass raw material to the glycerol is (1:5) - (1: 15);

(2) cooling the cooking liquor, and filtering to obtain a cellulose-rich matrix and a first filtrate;

mixing and washing the substrate and a low-boiling-point organic solvent, and filtering to obtain a second filtrate;

mixing the first filtrate and the second filtrate to obtain a combined solution, and then carrying out microfiltration on the combined solution by adopting a microfiltration membrane to obtain a microfiltration solution;

(3) and (3) carrying out ultrafiltration on the micro-filtrate by adopting an ultrafiltration membrane to obtain trapped fluid and ultrafiltrate, and adjusting the pH of the trapped fluid to 2.0-3.0 to obtain a product containing lignin.

The method for purifying the lignin from the agriculture and forestry biomass raw materials is simple, and has the following specific advantages:

1) the cooking liquor is filtered twice to improve the content of lignin in the combined liquor, thereby being beneficial to improving the yield of the lignin.

2) In the process of obtaining the second filtrate through suction filtration treatment, the low-boiling-point organic solvent is adopted for dilution, so that lignin remaining in the matrix can be eluted into the second filtrate as much as possible, the subsequent reduction of the viscosity of glycerol in the combined solution is facilitated, the combined solution can conveniently pass through a microfiltration membrane and an ultrafiltration membrane, and the filter membrane is not easy to block. In addition, compared with water, the organic solvent with low boiling point is favorable for subsequent evaporation and recycling.

3) The lignin purification mode breaks through the traditional mode that a large amount of acid liquor is needed for purification, only a microfiltration membrane and an ultrafiltration membrane with small pore diameters are needed for interception, the intercepted liquid containing a large amount of lignin can be intercepted, and then a small amount of acid liquor is used for adjusting the pH value of the intercepted liquid, so that the product containing the lignin can be obtained. The method avoids the use of a large amount of acid liquor, can meet the requirement of environmental protection and has low cost.

4) The lignin purification method has the advantage that the lignin purification degree in the lignin-containing product obtained by purification is high.

In one embodiment, after the step (3), distilling the ultrafiltrate to obtain ethanol and recoverable glycerol is further included.

In one embodiment, the low boiling point organic solvent is selected from at least one of methanol, ethanol, formic acid, acetic acid, acetone, ethyl formate, and ethyl acetate.

In one embodiment, the mass-to-volume ratio of the matrix to the low-boiling organic solvent is (1:5) - (1: 20).

In one embodiment, the temperature of the cooking treatment is 150-240 ℃, and the time of the cooking treatment is 15-120 min.

In one embodiment, the pressure of the ultrafiltration is 0.05-0.3MP and the temperature of the ultrafiltration is 25-80 ℃.

In one embodiment, the ultrafiltration membrane is made of a PL-based cellulose membrane.

In one embodiment, the pore size of the microfiltration membrane is 0.4 to 70 μm.

In one embodiment, the ultrafiltration membrane has a molecular weight cut-off of 500-7000 Da.

Detailed Description

The present invention will be described in detail with reference to the following embodiments in order to make the aforementioned objects, features and advantages of the invention more comprehensible. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

The invention provides a method for purifying lignin from an agricultural and forestry biomass raw material, which comprises the following steps:

(1) mixing an agricultural and forestry biomass raw material and glycerol to obtain a mixed solution, and performing high-temperature treatment under the alkali catalysis condition to obtain a cooking liquor, wherein the mass ratio of the agricultural and forestry biomass raw material to the glycerol is (1:5) - (1: 15).

It is to be understood that the term "agricultural and forestry biomass feedstock" as used herein refers to a feedstock containing lignocellulose.

In one embodiment, the agricultural and forestry biomass raw material is waste material after pretreatment operation, namely, the raw material is dried in an oven at 105 ℃ to constant weight after being screened by a 40-mesh sieve.

In one embodiment, the temperature of the cooking treatment is 150-240 ℃, and the time of the cooking treatment is 15-120 min. The normal-pressure short-time cooking mode can selectively remove most of lignin in the agriculture and forestry biomass raw materials.

It is understood that the agricultural and forestry biomass raw material source selected by the invention is not limited too much, for example: bagasse, and the glycerol can be industrial glycerol with low cost.

(2) Cooling the cooking liquor, and filtering to obtain a cellulose-rich matrix and a first filtrate;

mixing the substrate with a low-boiling-point organic solvent, and filtering to obtain a second filtrate;

and mixing the first filtrate and the second filtrate to obtain a combined solution, and then carrying out microfiltration on the combined solution by adopting a microfiltration membrane to obtain a microfiltration solution.

It is understood that the low boiling point organic solvent described in the present invention has a boiling point of 30 to 80 ℃.

In one embodiment, the low boiling point organic solvent is selected from at least one of methanol, ethanol, formic acid, acetic acid, acetone, ethyl formate, and ethyl acetate. Further, the low boiling point organic solvent is selected from ethanol.

In one embodiment, the mass-to-volume ratio of the matrix to the low-boiling organic solvent is (1:5) - (1: 20). The proportioning range is reasonable, and the lignin remaining in the matrix can be more easily eluted as much as possible.

In one embodiment, the pore size of the microfiltration membrane is 0.4 to 70 μm. Furthermore, the pore diameter of the micro-filtration membrane is 0.4-0.5 μm.

(3) And (3) carrying out ultrafiltration on the micro-filtrate by adopting an ultrafiltration membrane to obtain trapped fluid and ultrafiltrate, adjusting the pH of the trapped fluid to 2.0-3.0, and separating to obtain a product containing lignin.

It is understood that the retentate refers to the liquid that is retained without penetrating the ultrafiltration membrane. Ultrafiltrate refers to liquid that penetrates an ultrafiltration membrane.

In one embodiment, the pressure of the ultrafiltration is 0.08-0.3MP and the temperature of the ultrafiltration is 25-80 ℃.

In one embodiment, the ultrafiltration membrane has a molecular weight cut-off of 500-7000 Da.

In one embodiment, the ultrafiltration membrane is made of a PL-based cellulose membrane.

In one embodiment, after the step (3), evaporating the ultrafiltrate to obtain ethanol and glycerol. Wherein, the glycerol can be recycled as the preparation raw material in the cooking liquid again, and the ethanol can be further recycled.

In one embodiment, after the step (3), the method further comprises the steps of mixing the lignin-containing product with an acetic acid solution, adjusting the pH value to 1.8-2.2, performing acid precipitation, and drying to obtain refined lignin, wherein the lignin-containing product can be further purified by adopting an acid precipitation method, the purity of the lignin is improved, and the purity of the refined lignin can reach 90% -96%.

Further, the mass-to-volume ratio of the lignin-containing product to the acetic acid solution is (1:18) - (1: 22). The acetic acid solution is more beneficial to dissolving the lignin-containing product in the acetic acid solution, thereby facilitating the further purification of the subsequent lignin.

Further, the volume concentration of the acetic acid solution is 85% -95%.

The method for purifying the lignin from the agriculture and forestry biomass raw materials has the following advantages:

1) the cooking liquor is extracted twice, so that the content of lignin in the combined liquor is increased, and the yield of the lignin is improved. The low-boiling-point organic solvent is diluted, so that lignin remaining in the matrix can be eluted to the second filtrate as much as possible, the subsequent reduction of the viscosity of glycerol in the combined solution is facilitated, the combined solution can conveniently pass through a microfiltration membrane and an ultrafiltration membrane, and the filter membrane is not easy to block. In addition, compared with water, the organic solvent with low boiling point is favorable for subsequent evaporation and recycling.

3) The lignin purification mode breaks through the traditional mode that a large amount of acid liquor is needed for purification, only a microfiltration membrane and an ultrafiltration membrane with small pore diameters are needed for interception, the intercepted liquid containing a large amount of lignin can be intercepted, and then a small amount of acid liquor is used for adjusting the pH value of the intercepted liquid, so that the product containing the lignin can be obtained. The method avoids the use of a large amount of acid liquor, can meet the requirement of environmental protection and has low cost.

4) The lignin purification method has the advantage that the lignin purification degree in the lignin-containing product obtained by purification is high.

The method for purifying lignin from an agricultural and forestry biomass material according to the present invention will be described in detail with reference to the following examples.

Example 1

(1) 100g of oven-dried bagasse and 0.5kg of industrial glycerol were weighed into a 5L three-necked flask, 2.2g of sodium hydroxide was added to adjust the pH to 9.3, and the mixture was heated to 160 ℃ with stirring at 250rpm, and then heat-preserved and boiled for 20 minutes. And obtaining cooking liquor after the reaction is finished.

(2) And cooling the cooking liquor to 80 ℃, and performing suction filtration on the hot cooking liquor by using a G1 sand core funnel to respectively obtain a matrix rich in cellulose and a first filtrate. Stirring and mixing 800ml of ethanol and a matrix rich in cellulose, washing, then carrying out suction filtration again, mixing the first filtrate and the second filtrate to obtain a combined solution, carrying out suction filtration by using a G3 sand core funnel, carrying out reduced pressure suction filtration on the filtrate after suction filtration by using a microfiltration membrane of 0.45 mu m to obtain a micro-filtrate, and collecting the micro-filtrate.

(3) And (3) carrying out ultrafiltration treatment on the micro-filtrate by using a PL (polystyrene) cellulose membrane with the molecular weight cutoff of 1000Da under the conditions of the pressure of 0.3MP and the temperature of 30 ℃ to obtain a cutoff fluid and an ultrafiltrate.

(4) Adjusting the pH value of the trapped fluid to 2.0 by using hydrochloric acid to generate precipitate, separating and extracting by using a high-speed centrifuge at 4 ℃, washing with clear water to be neutral, and freeze-drying to obtain a product containing lignin.

(5) Dissolving the lignin-containing product in 90% acetic acid solution at a ratio of 1:20(w: v), adjusting pH to 2 with hydrochloric acid aqueous solution to realize acid precipitation, centrifuging, and freeze drying to obtain refined lignin.

(6) Collecting ultrafiltrate, performing rotary evaporation on a rotary evaporator to recover ethanol, mixing the recovered glycerol and industrial glycerol solvent at a volume ratio of 8:1, and performing the evaporation in the step (1) to prepare the cooking liquid again.

As a result: the purity of lignin in the lignin-containing product was 84%, the purity of lignin in the refined lignin was 92%, the refined lignin yield was 80%, and the recovery rates of ethanol and glycerol were 92% and 85%, respectively.

Example 2

(1) 100g of oven-dried bagasse and 1.2kg of industrial glycerol were weighed into a 5L three-necked flask, 1.3g of sodium hydroxide was added to adjust the pH to 8.5, and the mixture was heated to 220 ℃ with a stirring rate of 220rpm, and then heat-preserved and boiled for 25 minutes. And obtaining cooking liquor after the reaction is finished.

(2) And cooling the cooking liquor to 80 ℃, and performing suction filtration on the hot cooking liquor by using a G1 sand core funnel to respectively obtain a matrix rich in cellulose and a first filtrate. Mixing 950ml of ethanol and a matrix rich in cellulose by stirring, washing, performing suction filtration again to obtain a second filtrate, mixing the first filtrate and the second filtrate to obtain a combined solution, performing suction filtration by using a G3 sand core funnel, performing reduced pressure suction filtration on the filtrate after suction filtration by using a microfiltration membrane of 0.4 mu m to obtain a microfiltration solution, and collecting the microfiltration solution.

(3) And (3) carrying out ultrafiltration treatment on the micro-filtrate by using a PL cellulose membrane with the molecular weight cutoff of 6000Da under the conditions of the pressure of 0.2MP and the temperature of 40 ℃ to obtain a trapped fluid and an ultrafiltrate.

(4) Adjusting the pH value of the trapped fluid to 3.0 by using hydrochloric acid to generate precipitate, separating and extracting by using a high-speed centrifuge at 4 ℃, washing with clear water to be neutral, and freeze-drying to obtain a product containing lignin.

(5) Dissolving the lignin-containing product in 90% acetic acid solution at a ratio of 1:20(w: v), adjusting pH to 2 with hydrochloric acid aqueous solution to realize acid precipitation, centrifuging, and freeze drying to obtain refined lignin.

(6) Collecting ultrafiltrate, performing rotary evaporation on a rotary evaporator to recover ethanol, mixing the recovered glycerol and industrial glycerol solvent at a volume ratio of 9:1, and performing the evaporation in the step (1) to prepare the cooking liquid again.

As a result: the purity of lignin in the lignin-containing product was 82%, the purity of lignin in the refined lignin was 90%, the yield of refined lignin was 82%, and the recovery rates of ethanol and glycerol were 90% and 88%, respectively.

Example 3

(1) 100g of oven-dried bagasse and 1.4kg of industrial glycerol were weighed into a 5L three-necked flask, 4.2g of sodium hydroxide was added to adjust the pH to 11.5, and the mixture was heated to 240 ℃ with stirring at 500rpm, and then heat-preserved and boiled for 30 minutes. And obtaining cooking liquor after the reaction is finished.

(2) And cooling the cooking liquor to 80 ℃, and performing suction filtration on the hot cooking liquor by using a G1 sand core funnel to respectively obtain a matrix rich in cellulose and a first filtrate. Stirring and mixing 1100ml of ethanol and a matrix rich in cellulose, washing the matrix, then carrying out suction filtration again, mixing the first filtrate and the second filtrate to obtain a combined solution, carrying out suction filtration by using a G3 sand core funnel, carrying out reduced pressure suction filtration on the filtrate after suction filtration by using a microfiltration membrane of 70 mu m to obtain a microfiltration solution, and collecting the microfiltration solution.

(3) Performing ultrafiltration on the micro-filtrate by using a PL-based cellulose membrane with the molecular weight cutoff of 3000Da under the conditions of 0.15MP and 50 ℃ to obtain a cut-off solution and an ultrafiltrate.

(4) Adjusting the pH value of the trapped fluid to 2.5 by using hydrochloric acid to generate precipitate, separating and extracting by using a high-speed centrifuge at 4 ℃, washing with clear water to be neutral, and freeze-drying to obtain a product containing lignin.

(5) Dissolving the lignin-containing product in 90% acetic acid solution at a ratio of 1:20(w: v), adjusting pH to 2 with hydrochloric acid aqueous solution to realize acid precipitation, centrifuging, and freeze drying to obtain refined lignin.

(6) Collecting ultrafiltrate, performing rotary evaporation on a rotary evaporator to recover ethanol, mixing the recovered glycerol and industrial glycerol solvent at a volume ratio of 10:1, and performing the evaporation in the step (1) to prepare the cooking liquid again.

As a result: the purity of lignin in the lignin-containing product was 84%, the purity of lignin in the refined lignin was 94%, the yield of refined lignin was 86%, and the recovery rates of ethanol and glycerol were 94% and 82%, respectively.

The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.