CN104016948A - Method for preparing 2, 3-dihydro benzofuran by lignin low temperature pyrolysis - Google Patents

Abstract

The method for preparing 2,3-dihydrobenzofuran by low-temperature pyrolysis of lignin comprises: step 1: separating lignin raw material from dry raw material by enzymatic hydrolysis and mild acid hydrolysis; step 2: separating lignin raw material Place in a nitrogen environment, carry out pyrolysis reaction at a temperature of 250-360°C, and react for 0.5-1s to obtain 2,3-dihydrobenzofuran; this method can prepare lignin with high yield and high purity, Moreover, the structural damage to lignin is small, and 2,3-dihydrobenzofuran is produced from lignin under the condition of low-temperature pyrolysis, which has the characteristics of high yield, high purity and simple operation.

Description

Method for preparing 2,3-dihydrobenzofuran by low-temperature pyrolysis of lignin

technical field

The invention relates to a method for preparing 2,3-dihydrobenzofuran, in particular to a method for preparing 2,3-dihydrobenzofuran by low-temperature pyrolysis of lignin.

Background technique

Lignin (EMAL) is a high-molecular compound composed of phenylpropane units. It is an abundant natural organic resource second only to cellulose and widely exists in wood and gramineous plants. Lignin content (dry basis) is generally 20-40% in coniferous wood and hardwood, and 10-40% in different herbaceous plants, such as bagasse, corn stalks, peanut shells, rice husks and rice (wheat) Grass, Moso Bamboo, etc. Composed of grassy lignin petroleum guaiacol, syringol and p-propaphenol. The connections between basic structural units are mainly phenol ether bonds (1-4), and the thermochemical reactions of biomass and lignin pyrolysis chemical reactions mainly occur on such bonds.

The lignin separation technology includes the early strong inorganic acid method, the classic ground wood lignin separation method and the later cellulase degradation method. The lignin separation technology used in this patent is cellulase enzymatic hydrolysis/mild acid hydrolysis. The lignin prepared by this method has little structural damage, and the yield and purity can reach 50% and 95% respectively.

The pyrolysis of lignin isolated from air at high temperature can produce charcoal, tar and gas products. The yield of the product depends on a series of factors such as the chemical composition of lignin, the final temperature of the reaction, the heating rate and the structure of the equipment. Lignin has high thermal stability, and its thermal decomposition reaction generally occurs at 250-500°C. The pyrolysis oil formed during the pyrolysis of lignin mainly contains aromatic compounds and a small amount of acid.

2,3-Dihydrobenzofuran, commonly known as coumarin, is a pharmaceutical intermediate for the synthesis of some important drugs, and it is also a fine chemical raw material. Such as anti-tumor preparations, benzofuran sulfonylurea compounds, HIV protease inhibitor amino acid sulfonamide, matrix metalloproteinase inhibitor aryl sulfinamide hydroxamic acid, etc. At present, the preparation of 2,3-dihydrobenzofuran is usually synthesized by substituted ring method, which has low yield and cumbersome operation.

2,3-Dihydrobenzofuran is the main product of lignin pyrolysis, and the content of direct pyrolysis of biomass raw materials is very low.

Contents of the invention

In order to overcome the shortcomings of the above-mentioned prior art, the object of the present invention is to provide a method for producing 2,3-dihydrobenzofuran by low-temperature pyrolysis of lignin, which uses enzymatic hydrolysis and mild acid hydrolysis to separate lignin. Preparation of 2,3-dihydrobenzofuran under pyrolysis conditions has the characteristics of high yield, high purity and simple operation.

In order to achieve the above object, the technical scheme that the present invention takes is:

A method for preparing 2,3-dihydrobenzofuran by low-temperature pyrolysis of lignin, comprising:

Step 1: Using enzymatic hydrolysis and mild acid hydrolysis to separate the lignin raw material from the dry raw material;

Step 2: Put the lignin raw material in a nitrogen environment, and carry out a pyrolysis reaction at a temperature of 250-360° C. for 0.5-1 s to obtain 2,3-dihydrobenzofuran.

The first step includes: weighing 10g of ball-milled absolute-dry raw material, putting it into a 500mL conical flask with a stopper, adding 200mL of acetic acid/sodium acetate buffer solution, then adding 5g of cellulase, shaking well, putting on a stopper, and sealing Bottle mouth, fix the Erlenmeyer flask in a constant temperature incubator at 40°C, and cultivate it for 48 hours under the condition of shaking speed of 120r/min to obtain enzymatic crude lignin of carbohydrates;

After enzymatic hydrolysis treatment, centrifuge the mixture in the Erlenmeyer flask at room temperature at a speed of 5000r/min for 5 minutes. During centrifugation, wash the enzymatically hydrolyzed crude lignin with acidic deionized water with a pH value of 2.0 for 2-3 times ; The washed enzymatic crude lignin is transferred to a dry and clean plastic dish, and placed in a refrigerator to freeze into blocks; then transferred to a vacuum freezing environment for drying for 24 hours, and after drying, powdered absolute dry enzymatic crude lignin is obtained;

Weigh 5g of absolute-dried enzymatically hydrolyzed crude lignin, put it into a 250mL three-neck flask, add 100mL of acidic dioxane/water mixture, shake fully to mix the contents of the flask evenly;

Put the flask in the oil bath, connect the condenser tube and the nitrogen tube, fix the experimental device, seal the connection, open the pressure reducing valve of the nitrogen bottle and adjust the flow rate so that 2-3 Then, turn on the power supply of the oil bath, control the temperature at 87°C, and reflux and extract the mixed solution in the flask for 2 hours under the protection of nitrogen; Wash the filter residue with the mixed solution until the filtrate is clear, and collect the filtrate into the same beaker;

Add 0.595g sodium bicarbonate to carry out neutralization reaction in all filtrates collected, and stir 3h with magnetic stirrer;

The neutralized filtrate was transferred to a 50mL small flask, and the reduced-pressure rotary evaporation was carried out at a temperature of 30°C and a pressure of -0.1Mpa (the speed could be adjusted by itself), so that the volume of the filtrate was concentrated to about 3-5mL; then manually While stirring, slowly add to 2000mL acidic deionized water with a pH value of 2.0 to carry out flocculation and precipitation of lignin; after standing for 8 hours, remove the supernatant by siphon method;

After centrifuging the precipitated lignin at a speed of 5000r/min for 5min, washing with acidic deionized water with a pH value of 2.0 for 2-3 times, transferring the lignin to freeze into blocks, and freeze-drying; after freeze-drying The lignin is washed with n-hexane (chromatographic grade) to remove the remaining extract components in the lignin; the lignin after washing is vacuum-dried at room temperature with phosphorus pentoxide as a desiccant, that is, Obtain lignin raw material.

The dry raw materials are agricultural stalks and herbaceous materials, especially non-wood biomass such as moso bamboo, sugar cane and rice straw.

The enzyme activity of the cellulase is 1300 carboxymethyl cellulose enzyme activity units per milliliter.

The acidic dioxane/water mixture is a mixture of 1,4-dioxane and acidic deionized water with a pH value of 2.0 at a volume ratio of 85:15.

The dioxane/water mixture is a mixture of 1,4-dioxane and neutral deionized water at a volume ratio of 85:15.

The acidic deionized water is deionized water with a pH value of 2.0.

Working principle of the present invention is:

The method adopts cellulase enzymatic hydrolysis/mild acid hydrolysis technology to separate lignin, and then utilizes low-temperature pyrolysis technology to prepare 2,3-dihydrobenzofuran from lignin.

The beneficial effects of the present invention are:

The method can prepare lignin with high yield and high purity, and has little structural damage to lignin, and lignin can be prepared under low-temperature pyrolysis conditions to produce 2,3-dihydrobenzofuran, which has the advantages of high yield, The characteristics of high purity and simple operation. 2,3-Dihydrobenzofuran is a fine chemical raw material widely used in the synthesis of tricyclic compounds; it is also an important pharmaceutical synthesis intermediate, such as anti-tumor agents benzofuransulfonylurea compounds, HIV protease inhibitor amino acid isethionyl, matrix metalloproteinase inhibitor aryl sulfinamide hydroxamic acid, etc.

Description of drawings

Fig. 1 is the operation flowchart of separating and preparing EMAL.

Figure 2 is a total ion current (TIC) diagram of EMAL pyrolyzed fragments.

Figure 3 is the yield of pyrolysis products at different temperatures.

Detailed ways

The present invention will be described in further detail below in conjunction with the embodiments and accompanying drawings.

Referring to Fig. 1, the operation flow chart of separation and preparation of EMAL. The present invention is a method for preparing 2,3-dihydrobenzofuran by low-temperature pyrolysis of lignin, comprising:

Step 1: Using enzymatic hydrolysis and mild acid hydrolysis to separate the lignin raw material from the dry raw material;

Step 2: Put the lignin raw material in a nitrogen environment, and carry out a pyrolysis reaction at a temperature of 250-360° C. for 0.5-1 s to obtain 2,3-dihydrobenzofuran.

The first step includes: weighing 10g of ball-milled absolute-dry raw material, putting it into a 500mL conical flask with a stopper, adding 200mL of acetic acid/sodium acetate buffer solution, then adding 5g of cellulase, shaking well, putting on a stopper, and sealing Bottle mouth, fix the Erlenmeyer flask in a constant temperature incubator at 40°C, and cultivate it for 48 hours under the condition of shaking speed of 120r/min to obtain enzymatic crude lignin of carbohydrates;

After enzymatic hydrolysis treatment, centrifuge the mixture in the conical flask at room temperature at a speed of 5000r/min for 5min. Transfer the decomposed crude lignin to a dry and clean plastic dish, place it in the refrigerator to freeze into blocks; then transfer it to a vacuum freezing environment for drying for 24 hours, and obtain powdery absolute-dried enzymatically decomposed crude lignin after drying;

Weigh 5g of absolute-dried enzymatically hydrolyzed crude lignin, put it into a 250mL three-neck flask, add 100mL of acidic dioxane/water mixture, shake fully to mix the contents of the flask evenly;

Put the flask in the oil bath, connect the condenser tube and the nitrogen tube, fix the experimental device, seal the connection, open the pressure reducing valve of the nitrogen bottle and adjust the flow rate so that 2-3 Then, turn on the power supply of the oil bath, control the temperature at 87°C, and reflux and extract the mixed solution in the flask for 2 hours under the protection of nitrogen; Wash the filter residue with the mixed solution until the filtrate is clear, and collect the filtrate into the same beaker;

Add 0.595g sodium bicarbonate to carry out neutralization reaction in all filtrates collected, and stir 3h with magnetic stirrer;

The neutralized filtrate was transferred to a 50mL small flask, and the reduced-pressure rotary evaporation was carried out at a temperature of 30°C and a pressure of -0.1Mpa (the speed could be adjusted by itself), so that the volume of the filtrate was concentrated to about 3-5mL; then manually While stirring, slowly add to 2000mL acidic deionized water to carry out flocculation and precipitation of lignin; after standing for 8 hours, remove the supernatant by siphon method;

After centrifuging the precipitated lignin at a speed of 5000r/min for 5min, washing with acidic deionized water for 2-3 times, transferring the lignin to freeze into blocks, and freeze-drying; Washing with alkane (chromatographic grade) to remove the remaining extractive components in the lignin; the lignin after washing is vacuum-dried at room temperature with phosphorus pentoxide as a desiccant to obtain the lignin raw material.

The dry raw materials are agricultural stalks and herbaceous materials, especially non-wood biomass such as moso bamboo, sugar cane and rice straw.

The enzyme activity of the cellulase is 1300 carboxymethyl cellulose enzyme activity units per milliliter.

The acidic dioxane/water mixture is a mixture of 1,4-dioxane and acidic deionized water with a pH value of 2.0 at a volume ratio of 85:15.

The dioxane/water mixture is a mixture of 1,4-dioxane and neutral deionized water at a volume ratio of 85:15.

The acidic deionized water is deionized water with a pH value of 2.0.

Example 1

1) preparing lignin raw material;

Weigh 10g of the dry raw material of moso bamboo after ball milling, put it into a 500mL conical flask with a stopper, add 200mL of acetic acid/sodium acetate buffer solution and 5g of cellulase, shake well, cover with a stopper, seal the mouth of the bottle, put the conical flask Fixed in a constant temperature incubator at 40°C, cultivated for 48 hours under the condition of shaking speed of 120r/min, to obtain enzymatic crude lignin of carbohydrates;

After enzymatic hydrolysis treatment, centrifuge the mixture in the Erlenmeyer flask at room temperature at a speed of 5000r/min for 5 minutes. During centrifugation, wash the enzymatically hydrolyzed crude lignin with acidic deionized water with a pH value of 2.0 for 2-3 times ; The washed enzymatic crude lignin is transferred to a dry and clean plastic dish, placed in the refrigerator to freeze into blocks (glassware is easily cracked by freezing), and then transferred to a vacuum freezer environment for drying for 24 hours, and after drying, a powdery dry product is obtained. Enzymatic hydrolysis of crude lignin;

Weigh 5g of absolute-dried enzymatically hydrolyzed crude lignin, put it into a 250mL three-neck flask, add 100mL of acidic dioxane/water mixture, shake fully to mix the contents of the flask evenly;

Put the flask in the oil bath, connect the condenser tube and the nitrogen tube, fix the experimental device, seal the connection, open the pressure reducing valve of the nitrogen bottle and adjust the flow rate so that 2-3 Then, turn on the power supply of the oil bath, control the temperature at 87°C, and reflux and extract the mixed solution in the flask for 2 hours under the protection of nitrogen; Wash the filter residue with the mixed solution until the filtrate is clear, and collect the filtrate into the same beaker;

Add 0.595g sodium bicarbonate to carry out neutralization reaction in all filtrates collected, and stir 3h with magnetic stirrer;

The neutralized filtrate was transferred to a 50mL small flask, and the temperature was 30°C, and the pressure was -0.1Mpa. Under the environment of -0.1Mpa, the vacuum rotary evaporation was carried out (the rotation speed was adjusted by itself), and the volume of the filtrate was concentrated to about 3-5mL, and then Stir manually, slowly add to 2000mL acidic deionized water with a pH value of 2.0, carry out flocculation and precipitation of lignin, after standing for 8 hours, remove the supernatant by siphon method;

After centrifuging the precipitated lignin at a speed of 5000r/min for 5min, washing with acidic deionized water with a pH value of 2.0 for 2-3 times, transferring the lignin to freeze into blocks, and freeze-drying; after freeze-drying The lignin is washed with n-hexane (chromatographic grade) to remove the remaining extract components in the lignin; the lignin after washing is vacuum-dried at room temperature with phosphorus pentoxide as a desiccant, that is, Obtain lignin raw material.

2) Preparation of 2,3-dihydrobenzofuran

The lignin raw material is placed in a nitrogen environment, and the pyrolysis reaction is carried out at a temperature of 250-360°C for 0.5-1s to obtain 2,3-dihydrobenzofuran.

In this method, when the pyrolysis temperature is 250°C, the yield of 2,3-dihydrobenzofuran obtained is 55.66%; when the pyrolysis temperature is 320°C, the yield of 2,3-dihydrobenzofuran obtained is was 66.26%.

Example 2

1) preparing lignin raw material;

Weigh 10g of sugarcane dry raw material after ball milling, put it into a 500mL conical flask with a stopper, add 200mL of acetic acid/sodium acetate buffer solution and 5g of cellulase, shake well, cover with a stopper, seal the bottle mouth, and put the conical flask Fixed in a constant temperature incubator at 40°C, cultivated for 48 hours under the condition of shaking speed of 120r/min, to obtain enzymatic crude lignin of carbohydrates;

After enzymatic hydrolysis treatment, centrifuge the mixture in the Erlenmeyer flask at room temperature at a speed of 5000r/min for 5 minutes. During centrifugation, wash the enzymatically hydrolyzed crude lignin with acidic deionized water with a pH value of 2.0 for 2-3 times ; The washed enzymatic crude lignin is transferred to a dry and clean plastic dish, placed in a refrigerator to freeze into blocks, and then transferred to a vacuum freezing environment to dry for 24 hours, and after drying, powdery absolute dry enzymatic crude lignin is obtained;

Weigh 5g of absolute-dried enzymatically hydrolyzed crude lignin, put it into a 250mL three-neck flask, add 100mL of acidic dioxane/water mixture, shake fully to mix the contents of the flask evenly;

Put the flask in the oil bath, connect the condenser tube and the nitrogen tube, fix the experimental device, seal the connection, open the pressure reducing valve of the nitrogen bottle and adjust the flow rate so that 2-3 Then, turn on the power supply of the oil bath, control the temperature at 87°C, and reflux and extract the mixed solution in the flask for 2 hours under the protection of nitrogen; Wash the filter residue with the mixed solution until the filtrate is clear, and collect the filtrate into the same beaker;

Add 0.595g sodium bicarbonate to carry out neutralization reaction in all filtrates collected, and stir 3h with magnetic stirrer;

The neutralized filtrate was transferred to a 50mL small flask, and the temperature was 30°C, and the pressure was -0.1Mpa. Under the environment of -0.1Mpa, the vacuum rotary evaporation was carried out (the rotation speed was adjusted by itself), and the volume of the filtrate was concentrated to about 3-5mL, and then Stir manually, slowly add to 2000mL acidic deionized water with a pH value of 2.0, carry out a large amount of flocculation and precipitation of lignin, after standing for 8 hours, remove the supernatant by siphon method;

After centrifuging the precipitated lignin at a speed of 5000r/min for 5min, washing with acidic deionized water with a pH value of 2.0 for 2-3 times, transferring the lignin to freeze into blocks, and freeze-drying; after freeze-drying The lignin is washed with n-hexane (chromatographic grade) to remove the remaining extractive components in the lignin;

The lignin after washing is vacuum-dried at room temperature with phosphorus pentoxide as a desiccant to obtain the lignin raw material.

2) Preparation of 2,3-dihydrobenzofuran

The lignin raw material is placed in a nitrogen environment, and the pyrolysis reaction is carried out at a temperature of 250-360°C for 0.5-1s to obtain 2,3-dihydrobenzofuran.

In this method, when the pyrolysis temperature is 250°C, the yield of 2,3-dihydrobenzofuran obtained is 55.04%; when the pyrolysis temperature is 320°C, the yield of 2,3-dihydrobenzofuran obtained is was 65.04%.

Figure 2 The total ion current (TIC) diagram of EMAL pyrolyzed fragments. As the pyrolysis temperature increases, the number of proton peaks of pyrolysis products increases, which means that the types and quantities of pyrolysis products increase.

Figure 3 is the yield of pyrolysis products at different temperatures. As shown in the figure, the yields of benzofuran at pyrolysis temperatures of 250°C, 320°C, 400°C, 600°C, and 800°C are 55.66%, 66.26%, 56.62%, 36.05%, and 19.15%, respectively. In the figure, DHBF is the abbreviation of 2,3-dihydrobenzofuran.

Claims (7)

1. The method for preparing 2,3-dihydrobenzofuran by low-temperature pyrolysis of lignin, is characterized in that, comprising: Step 1: Using enzymatic hydrolysis and mild acid hydrolysis to separate the lignin raw material from the dry raw material; Step 2: Put the lignin raw material in a nitrogen environment, and carry out a pyrolysis reaction at a temperature of 250-360° C. for 0.5-1 s to obtain 2,3-dihydrobenzofuran. 2. the method for producing 2,3-dihydrobenzofuran by low temperature pyrolysis of lignin according to claim 1, is characterized in that, described step 1 comprises: Weigh 10g of dry raw material after ball milling, put it into a 500mL Erlenmeyer flask with a stopper, add 200mL of acetic acid/sodium acetate buffer solution, then add 5g of cellulase, shake well, cover with a stopper, seal the mouth of the bottle, and put the conical The bottle was fixed in a constant temperature incubator at 40°C, and cultured for 48 hours at a shaking speed of 120r/min to obtain enzymatically hydrolyzed crude lignin from carbohydrates; After enzymatic hydrolysis treatment, centrifuge the mixture in the conical flask at room temperature at a speed of 5000r/min for 5min. Transfer the decomposed crude lignin to a dry and clean plastic dish, place it in the refrigerator to freeze into blocks; then transfer it to a vacuum freezing environment for drying for 24 hours, and obtain powdery absolute-dried enzymatically decomposed crude lignin after drying; Weigh 5g of absolute-dried enzymatically hydrolyzed crude lignin, put it into a 250mL three-neck flask, add 100mL of acidic dioxane/water mixture, shake fully to mix the contents of the flask evenly; Put the flask in the oil bath, connect the condenser tube and the nitrogen tube, fix the experimental device, seal the connection, open the pressure reducing valve of the nitrogen bottle and adjust the flow rate so that 2-3 Then, turn on the power supply of the oil bath, control the temperature at 87°C, and reflux and extract the mixed solution in the flask for 2 hours under the protection of nitrogen; Wash the filter residue with the mixed solution until the filtrate is clear, and collect the filtrate into the same beaker; Add 0.595g sodium bicarbonate to carry out neutralization reaction in all filtrates collected, and stir 3h with magnetic stirrer; The neutralized filtrate was transferred to a 50mL small flask, and the reduced-pressure rotary evaporation was carried out at a temperature of 30°C and a pressure of -0.1Mpa (the speed could be adjusted by itself), so that the volume of the filtrate was concentrated to about 3-5mL; then manually While stirring, slowly add to 2000mL acidic deionized water to carry out flocculation and precipitation of lignin; after standing for 8 hours, remove the supernatant by siphon method; After centrifuging the precipitated lignin at a speed of 5000r/min for 5min, washing with acidic deionized water for 2-3 times, transferring the lignin to freeze into blocks, and freeze-drying; Washing with alkane (chromatographic grade) to remove the remaining extractive components in the lignin; the lignin after washing is vacuum-dried at room temperature with phosphorus pentoxide as a desiccant to obtain the lignin raw material. 3. The method for producing 2,3-dihydrobenzofuran by low-temperature pyrolysis of lignin according to claim 1 or 2, characterized in that: the absolute-dry raw material is agricultural straw and herbs, especially including : Moso bamboo, sugar cane, rice straw and other non-wood biomass. 4. The method for producing 2,3-dihydrobenzofuran by low-temperature pyrolysis of lignin according to claim 1 or 2, characterized in that: the enzyme activity of the cellulase is 1300 carboxymethylcellulose Enzyme activity units per milliliter. 5. The method for producing 2,3-dihydrobenzofuran by low-temperature pyrolysis of lignin according to claim 2, characterized in that: the acidic dioxane/water mixture is 1,4-diox A mixture of hexacyclic and acidic deionized water with a pH value of 2.0 at a volume ratio of 85:15. 6. The method for preparing 2,3-dihydrobenzofuran by low-temperature pyrolysis of lignin according to claim 2, characterized in that: the dioxane/water mixture is 1,4-dioxane A mixture of ring and neutral deionized water at a volume ratio of 85:15. 7. The method for preparing 2,3-dihydrobenzofuran by low-temperature pyrolysis of lignin according to claim 2, characterized in that: the acidic deionized water is deionized water with a pH value of 2.0.