阅读说明：本技术 一种基于双相溶剂体系的玉米秸秆转化乙酰丙酸乙酯及提取木质素的方法 (Method for converting corn straw into ethyl levulinate and extracting lignin based on two-phase solvent system ) 是由 张芹芹 林晓琪 韩德志 陈维胜 姜开森 于 2021-01-21 设计创作，主要内容包括：本发明公开了一种基于双相溶剂体系的玉米秸秆转化乙酰丙酸乙酯及提取木质素的方法,包括以下步骤：将玉米秸秆粉、离子液体、乙醇、水、三氯甲烷混合,在温度为180-220℃、压力为2-4MPa的条件下反应20-45min,反应后经孔径为10-20微米的定性滤纸抽滤,得滤液一；向滤液一中加水,静置4-6h后离心分离,得滤渣木质素和滤液二,将滤液二经过逐级旋蒸获得最终馏分即乙酰丙酸乙酯。本发明双相溶剂体系为乙醇-水和三氯甲烷的两相体系,本发明通过双相溶剂体系做溶剂,生成的乙酰丙酸乙酯从乙醇-水相中转移到三氯甲烷相中,有利于提高乙酰丙酸乙酯的转化率,降低产物分离的难度。(The invention discloses a method for converting corn straw into ethyl levulinate and extracting lignin based on a two-phase solvent system, which comprises the following steps: mixing the corn straw powder, the ionic liquid, ethanol, water and chloroform, reacting for 20-45min at the temperature of 180-220 ℃ and under the pressure of 2-4MPa, and performing suction filtration through qualitative filter paper with the aperture of 10-20 microns after reaction to obtain a first filtrate; adding water into the filtrate I, standing for 4-6h, centrifuging to obtain filter residue lignin and filtrate II, and performing stepwise rotary evaporation on the filtrate II to obtain the final fraction ethyl levulinate. The two-phase solvent system is a two-phase system of ethanol-water and trichloromethane, and the generated ethyl levulinate is transferred into the trichloromethane phase from the ethanol-water phase by taking the two-phase solvent system as a solvent, so that the conversion rate of the ethyl levulinate is improved, and the difficulty of product separation is reduced.)

1. A method for converting corn straw into ethyl levulinate and extracting lignin based on a two-phase solvent system is characterized by comprising the following steps:

(1) mixing the corn straw powder, the ionic liquid, ethanol, water and chloroform, reacting for 20-45min at the temperature of 180-220 ℃ and under the pressure of 2-4MPa, and performing suction filtration through qualitative filter paper with the aperture of 10-20 microns after reaction to obtain a first filtrate;

(2) adding water into the filtrate I, standing for 4-6h, centrifuging to obtain filter residue lignin and filtrate II, and sequentially subjecting the filtrate II to atmospheric distillation at 80 ℃, vacuum distillation at 80-120 ℃ and vacuum distillation at 120-160 ℃ to obtain the final fraction ethyl levulinate.

2. The method for converting ethyl levulinate into corn straw and extracting lignin based on a two-phase solvent system according to claim 1, wherein the preparation method of the corn straw powder comprises the following steps: cleaning the corn straws with water, and then naturally drying, crushing and sieving to obtain the corn straw powder with the particle size of less than 60 meshes.

3. The method for converting ethyl levulinate into corn stover and extracting lignin according to claim 1, wherein the ionic liquid is any one of 1-methyl-3-propanesulfonic acid hydrogen sulfate, 1-methyl-3-propanesulfonic acid chloride, 1-methyl-3-propanesulfonic acid hydrogen phosphate or 1-methyl-3-propyl hydrogen sulfate.

4. The method for converting corn stalk into ethyl levulinate and extracting lignin based on the two-phase solvent system of claim 1, wherein in the step (1), per 1g of corn stalk powder, the following components are added: 40-60ml of ethanol, 10-20ml of water and 40-70ml of trichloromethane, wherein the total volume of the ethanol, the water and the trichloromethane is 120 ml.

5. The method for converting corn stalk into ethyl levulinate and extracting lignin based on the two-phase solvent system of claim 4, wherein in the step (1), 0.5-2.5mmol of ionic liquid is added to every 1g of corn stalk powder.

6. The method for converting corn stover into ethyl levulinate and extracting lignin based on a biphasic solvent system according to claim 1, wherein in the step (2), the volume ratio of the first filtrate to the water is 1: 4-6.

7. The method for converting corn stover into ethyl levulinate and extracting lignin according to claim 1, wherein in step (2), the rotation speed of the centrifugal separation is 5000 rpm, and the time of the centrifugal separation is 15 minutes.

Technical Field

The invention belongs to the technical field of agricultural and sideline product deep processing and catalytic liquefaction system design, and particularly relates to a method for converting corn straw into ethyl levulinate and extracting lignin based on a two-phase solvent system.

Background

The large consumption of conventional fossil fuels leads to a drastic drop in fuel reserves, a rapid increase in global energy consumption, and an increase in environmental deterioration. Therefore, international society has been working on developing renewable energy sources such as biomass, solar energy, thermal energy, tides, wind energy, water power, and the like. Among them, biomass is considered the only carbon-based renewable resource, such as agriculture and forestry biomass. It produces good environmental benefits from a green and sustainable point of view to reduce excessive carbon emissions from chemicals and liquid fuel production. Where the use of edible crops for energy and materials would compete with the production of food products as raw materials, more and more researchers are turning their attention to the use of waste biomass. China is a big agricultural country, and various crop straws have large yield, wide distribution and various types and are valuable resources for agricultural development for a long time.

At present, the corn straws are mainly used as feed and are combusted in China, and the utilization value of the corn straws is not fully exerted. The corn stalks mainly comprise cellulose, hemicellulose and lignin, wherein the cellulose and the hemicellulose comprise hexose and pentose and can be converted into an important platform compound, namely ethyl levulinate, through hydrolysis and esterification. Ethyl levulinate is a common fatty acid ester, can be used as a substitute of petroleum-based chemicals, and is used in the industries of biofuel additives, foods, cosmetics, decorative coatings, medical drugs and the like. At present, the conversion of the woody biomass into the ethyl levulinate is mainly catalyzed by a traditional strong acid. However, there are the following problems: firstly, the conversion efficiency of cellulose and hemicellulose in the corn straws is low, and secondly, lignin is wasted; thirdly, the product is difficult to separate; fourthly, the catalyst can not be recycled.

Therefore, the technical personnel in the field need to solve the problems of improving the conversion rate of converting the corn straws into the ethyl levulinate and reducing the difficulty of separating the products and effectively extracting the lignin in the corn straws.

Disclosure of Invention

In view of the above, the invention provides a method for converting corn stalks into ethyl levulinate and extracting lignin based on a two-phase solvent system.

In order to achieve the purpose, the invention adopts the following technical scheme:

a method for converting corn straw into ethyl levulinate and extracting lignin based on a two-phase solvent system comprises the following steps:

(1) mixing the corn straw powder, the ionic liquid, ethanol, water and chloroform, reacting for 20-45min at the temperature of 180-220 ℃ and under the pressure of 2-4MPa, and performing suction filtration through qualitative filter paper with the aperture of 10-20 microns after reaction to obtain a first filtrate;

(2) adding water into the filtrate I, standing for 4-6h, centrifuging to obtain filter residue lignin and filtrate II, and sequentially subjecting the filtrate II to atmospheric distillation at 80 ℃, vacuum distillation at 80-120 ℃ and vacuum distillation at 120-160 ℃ to obtain the final fraction ethyl levulinate.

Further, the preparation method of the corn straw powder comprises the following steps: cleaning the corn straws with water, and then naturally drying, crushing and sieving to obtain the corn straw powder with the particle size of less than 60 meshes.

The beneficial effects of the further technical scheme are that: the liquefaction process is strengthened, and the conversion efficiency of the product is improved.

Further, the ionic liquid is any one of 1-methyl-3-propyl sulfonic acid hydrogen sulfate, 1-methyl-3-propyl sulfonic acid chloride, 1-methyl-3-propyl sulfonic acid hydrogen phosphate and 1-methyl-3-propyl sulfuric acid hydrogen salt.

The beneficial effects of the further technical scheme are that: promoting the product conversion, and recycling the ionic liquid.

Further, in the step (1), every 1g of the corn straw powder is added with: 40-60ml of ethanol, 10-20ml of water and 40-70ml of trichloromethane, wherein the total volume of the ethanol, the water and the trichloromethane is 120 ml.

The beneficial effects of the further technical scheme are that: the solvent is brought into a two-phase state, which promotes the separation of lignin and the forward conversion of the product.

Further, in the step (1), 0.5-2.5mmol of ionic liquid is added to every 1g of the corn straw powder.

The beneficial effects of the further technical scheme are that: the yield of the ethyl levulinate is improved.

Further, in the step (2), the volume ratio of the filtrate I to the water is 1: 4-6.

The beneficial effects of the further technical scheme are that: so that the lignin is completely precipitated.

Further, in the step (2), the rotation speed of the centrifugal separation is 5000 rpm, and the time of the centrifugal separation is 15 minutes.

The invention has the beneficial effects that: the two-phase solvent system is a two-phase system of ethanol-water and trichloromethane, and the generated ethyl levulinate is transferred into the trichloromethane phase from the ethanol-water phase by taking the two-phase solvent system as a solvent, so that the conversion rate of the ethyl levulinate is improved, and the difficulty of product separation is reduced.

The invention converts cellulose and semi-fiber in the corn straw into ethyl levulinate under the catalytic action of the ionic liquid, and the ionic liquid is easy to recover and recycle for many times.

The method effectively extracts the lignin in the corn straws by using an ethanol-water and trichloromethane double-phase solvent system, thereby avoiding the waste of the lignin.

Drawings

FIG. 1 is a flow chart of a process for converting corn stalks into ethyl levulinate and extracting lignin based on a two-phase solvent system according to the present invention;

in the figure: 1-a mechanical stirring device; 2-a pressure gauge; 3-high pressure reactor; 4-polytetrafluoroethylene lining; a 5-water-ethanol phase; 6-trichloromethane phase; 7-beaker; 8-a thermocouple;

FIG. 2 is a GC-MS chromatogram of ethyl levulinate provided in example 1 of the present invention;

FIG. 3 is a gas chromatogram of ethyl levulinate provided in example 1 of the present invention;

FIG. 4 is a gas chromatogram of ethyl levulinate provided in example 2 of the present invention;

FIG. 5 is a gas chromatogram of ethyl levulinate provided in example 3 of the present invention;

fig. 6 is a gas chromatogram of ethyl levulinate provided in example 4 of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1

Adding 4g of corn stalk powder, 4mmol of 1-methyl-3-propanesulfonic acid hydrogen sulfate, 10mL of deionized water, 40mL of ethanol and 70mL of trichloromethane into a 250mL high-temperature high-pressure reaction kettle with a stirrer, a thermocouple and a polytetrafluoroethylene lining, heating to 200 ℃ and reacting under the pressure of 3MPa for 45 minutes, stopping stirring and heating, putting the reaction kettle into cold water, quickly cooling to room temperature, pouring the cold water into a Buchner funnel which is already provided with 2 layers of filter paper with the aperture of 10-20 micrometers, carrying out suction filtration, washing with ethanol for multiple times to obtain residue and filtrate I, wherein the residue rate is 92.79%, adding 400mL of water into the filtrate I, standing for 4 hours, carrying out centrifugal separation to obtain dark brown precipitated lignin and filtrate II, carrying out centrifugal separation at the rotating speed of 5000 revolutions per minute for 15 minutes, keeping the filtrate II in a two-phase state, and carrying out gas chromatography analysis on the separated lower trichloromethane phase, the content of the obtained ethyl levulinate is 26.78%, and the final fraction, namely the ethyl levulinate, is obtained by distilling the trichloromethane at the temperature of 80 ℃ under normal pressure, distilling at the temperature of 80 ℃ under reduced pressure and distilling at the temperature of 120 ℃ under reduced pressure in sequence.

The residue rate calculation method comprises the following steps:

the method for calculating the yield of the ethyl levulinate comprises the following steps:

example 2

Adding 4g of corn stalk powder, 6mmol of 1-methyl-3-propanesulfonic acid hydrogen sulfate, 15mL of deionized water, 45mL of ethanol and 60mL of trichloromethane into a 250mL high-temperature high-pressure reaction kettle with a stirrer, a thermocouple and a polytetrafluoroethylene lining, heating to 210 ℃ and reacting for 45 minutes under the pressure of 4MPa, stopping stirring and heating, putting the reaction kettle into cold water, quickly cooling to room temperature, pouring the cold water into a Buchner funnel which is provided with 2 layers of filter paper with the aperture of 10-20 micrometers, carrying out suction filtration, washing with ethanol for multiple times to obtain residue and filtrate I, wherein the residue rate is 96.95%, adding 400mL of water into the filtrate, standing for 5 hours, carrying out centrifugal separation to obtain dark brown precipitated lignin and filtrate II, carrying out centrifugal separation at the rotating speed of 5000 revolutions per minute for 15 minutes, keeping the filtrate II in a two-phase state, carrying out gas chromatography analysis on the separated lower trichloromethane phase, the content of the obtained ethyl levulinate is 28.62%, and the final fraction, namely the ethyl levulinate, is obtained by distilling the trichloromethane at the temperature of 80 ℃ and the normal pressure, distilling at the temperature of 100 ℃ and distilling at the temperature of 140 ℃ and the reduced pressure in sequence.

Example 3

Adding 4g of corn stalk powder, 4mmol of 1-methyl-3-propanesulfonic acid hydrogen sulfate, 10mL of deionized water, 40mL of ethanol and 70mL of trichloromethane into a 250mL high-temperature high-pressure reaction kettle with a stirrer, a thermocouple and a polytetrafluoroethylene lining, heating to 220 ℃ and reacting for 30 minutes under the pressure of 4MPa, stopping stirring and heating, putting the reaction kettle into cold water, quickly cooling to room temperature, pouring the cold water into a Buchner funnel which is already provided with 2 layers of filter paper with the aperture of 10-20 micrometers, carrying out suction filtration, washing with ethanol for multiple times to obtain residue and filtrate I, wherein the residue rate is 85.31%, adding 400mL of water into the filtrate I, standing for 6 hours, carrying out centrifugal separation to obtain dark brown precipitated lignin and filtrate II, carrying out centrifugal separation at the rotating speed of 5000 revolutions per minute for 15 minutes, keeping the filtrate II in a two-phase state, and carrying out gas chromatography analysis on the separated lower trichloromethane phase, the content of the ethyl levulinate is 25.47%, and the final fraction, namely the ethyl levulinate, is obtained by distilling the trichloromethane at the temperature of 80 ℃ and the normal pressure, distilling at the temperature of 120 ℃ and distilling at the temperature of 160 ℃ and the reduced pressure in sequence.

Example 4

Adding 4g of corn stalk powder, 4mmol of 1-methyl-3-propanesulfonic acid bisulfate, 20mL of deionized water, 60mL of ethanol and 40mL of trichloromethane into a 250mL high-temperature high-pressure reaction kettle with a stirrer, a thermocouple and a polytetrafluoroethylene lining, heating to 220 ℃ and reacting under 4MPa for 25 minutes, stopping stirring and heating, putting the reaction kettle into cold water for rapidly cooling to room temperature, pouring the cold water into a Buchner funnel which is already filled with 2 layers of filter paper with the aperture of 10-20 micrometers for suction filtration, washing the filter liquor for multiple times by using ethanol to obtain residue and filtrate I, wherein the residue rate is 82.53%, adding 400mL of water into the filtrate I, standing for 6 hours, performing centrifugal separation to obtain dark brown precipitated lignin and filtrate II, performing centrifugal separation at the rotating speed of 5000 revolutions per minute for 15 minutes, and keeping the filtrate II in a two-phase state, and performing gas chromatography on the separated lower trichloromethane phase, the content of the ethyl levulinate is 19.46 percent, and the final fraction, namely the ethyl levulinate, is obtained by distilling the trichloromethane sequentially at the normal pressure of 80 ℃, then distilling at the reduced pressure of 120 ℃ and distilling at the reduced pressure of 160 ℃.

The description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.