阅读说明：本技术 一种糠醛的精制方法 (Refining method of furfural ) 是由 蔡卫滨 王泽众 钱建兵 范子久 于 2021-09-23 设计创作，主要内容包括：本发明提供了一种由毛醛制备高纯度糠醛的精制方法,属于化工提纯领域。本发明提供的精制方法,首先利用脱轻塔进行一级精馏,除去毛醛中的甲醇、水、醋酸等轻组分,然后再利用精制塔进行二级精馏,除去2-乙酰呋喃和5-甲基糠醛等重组分。本发明采用双塔连续精馏,提高了处理能力,产品稳定性更可控；通过控制脱轻塔和精制塔的理论塔板数、进料位置和回流比,较完全除去轻组分和重组分的含量,最终得到高纯度的优质糠醛产品。本发明提供的糠醛精制方法,可有效去除糠醛中的轻、重组分,得到纯度达99.99％的高纯度优质糠醛。(The invention provides a refining method for preparing high-purity furfural from crude aldehyde, and belongs to the field of chemical purification. The refining method provided by the invention comprises the steps of firstly utilizing a light component removal tower to carry out primary rectification to remove light components such as methanol, water, acetic acid and the like in the crude aldehyde, and then utilizing a refining tower to carry out secondary rectification to remove heavy components such as 2-acetylfuran, 5-methylfurfural and the like. The invention adopts double-tower continuous rectification, improves the processing capacity and has more controllable product stability; by controlling the theoretical plate number, the feeding position and the reflux ratio of the light component removal tower and the refining tower, the contents of light components and heavy components are completely removed, and finally a high-purity high-quality furfural product is obtained. The furfural refining method provided by the invention can effectively remove light and heavy components in furfural to obtain high-purity high-quality furfural with the purity of 99.99%.)

1. A method for refining furfural comprises the following steps:

(1) performing primary rectification on the wool aldehyde by using a light component removal tower, and then extracting a primary material from a tower kettle of the light component removal tower;

the number of theoretical plates of the light component removal tower is 5-14;

the feeding position of the crude aldehyde is the 1 st to 5 th theoretical tower plates from top to bottom in the light component removal tower;

(2) performing secondary rectification on the primary material obtained in the step (1) by using a refining tower, and then extracting at the top of the refining tower to obtain a finished product furfural;

the theoretical plate number of the refining tower is 21-35, and the reflux ratio of the refining tower is 1-3;

the feeding position of the first-stage material is 12 th to 25 th theoretical plates from top to bottom in the refining tower.

2. The production process according to claim 1, wherein the number of theoretical plates of the light ends removal column in the step (1) is 8 to 12.

3. The production method according to claim 1, wherein the feed position of the maaldehyde in the step (1) is 2 to 3 theoretical plates from top to bottom in the lightness-removing column.

4. The preparation method according to claim 1, wherein the maxaldehyde in the step (1) is crude furfural which has been deacidified by water washing or alkali washing.

5. The production process according to claim 1, wherein the overhead temperature of the lightness-removing column in the step (1) is 30 to 70 ℃ and the overhead pressure of the lightness-removing column is 3 to 25 kPa.

6. The production process according to claim 1, wherein the mass of the overhead product of the light ends removal column in the step (1) is 0.8 to 1.2 times the amount of the feed to the light ends removal column; and condensing and separating distillate at the tower top in sequence to obtain a water phase and an oil phase, extracting the water phase into a water-aldehyde tank, and completely refluxing the oil phase into the light component removal tower.

7. The production process according to claim 1, wherein the number of theoretical plates of the purification column in the step (2) is from 26 to 34, and the reflux ratio of the purification column is from 1.5 to 2.5.

8. The method according to claim 1, wherein the feed position of the primary material in the step (2) is 14 to 24 theoretical plates from top to bottom in the refining column.

9. The production method according to claim 1, wherein the temperature at the top of the purification column in the step (2) is 75 to 115 ℃ and the pressure at the top of the purification column is 3 to 25 kPa.

Technical Field

The invention relates to the field of chemical purification, in particular to a furfural refining method.

Background

Furfural is also called 2-furaldehyde and is active in chemical property. Furfural, the most important derivative of furan ring systems, can be used to produce numerous chemical products with high added value by oxidation, condensation and other reactions, and is widely used in the industries of synthetic rubber, resin, paint, medicine, pesticide and the like.

The general furfural production process mainly comprises the steps of hydrolyzing biomass to obtain crude furfural, and refining and purifying to obtain the finished furfural. The crude aldehyde contains light components such as methanol and acetic acid and heavy components such as 2-acetylfuran and 5-methylfurfural besides water.

With the development of the technology for preparing aviation kerosene from biomass raw materials, the demand of high-quality furfural is continuously increased, and higher requirements are put on the purity of furfural, wherein the content of light components such as methanol, water and acetic acid and the content of impurities such as 2-acetylfuran and 5-methylfurfural need to be as low as possible so as to improve the purity of furfural.

Wherein, the difficulty of removing most light components is not great, but the difficulty is great when the concentration of the light components is reduced to be below 0.1 percent; among heavy components, 5-methylfurfural has certain difficulty in separation, 2-acetylfuran is more difficult to separate due to the fact that the boiling point of the 2-acetylfuran is closer to that of furfural, and the 2-acetylfuran is difficult to remove when the number of theoretical plates is limited and the operation parameters are unreasonable in setting. In addition, the furfural refining mostly adopts a single-tower batch distillation process at present, the processing capacity is limited, the single processing period is long, the product purity is greatly influenced by the extraction time, the stability of the product quality is difficult to ensure, the removal rate of light components is limited, the separation performance of the 2-acetylfuran is basically avoided, and the product purity is difficult to meet the latest requirement.

Disclosure of Invention

The invention aims to provide a furfural refining method, which improves the processing capacity, has more controllable product stability, can effectively remove light components such as methanol, water and acetic acid and heavy components such as 2-acetylfuran and 5-methylfurfural contained in the furfural, improves the quality of furfural products, and obtains high-quality furfural products with the purity of 99.99 percent.

In order to achieve the above object, the present invention provides the following technical solutions:

the invention provides a furfural refining method, which comprises the following steps:

(1) performing primary rectification on the wool aldehyde by using a light component removal tower, and then extracting a primary material from a tower kettle of the light component removal tower;

the number of theoretical plates of the light component removal tower is 5-14;

the feeding position of the crude aldehyde is the number 1-5 theoretical plates from top to bottom in the light component removal tower;

(2) performing secondary rectification on the primary material obtained in the step (1) by using a refining tower, and then extracting at the top of the refining tower to obtain a finished product furfural;

the theoretical plate number of the refining tower is 21-35, and the reflux ratio of the refining tower is 1-3;

the feeding position of the first-stage material is 12 th to 25 th theoretical plates from top to bottom in the refining tower.

Preferably, the number of theoretical plates of the light component removal tower in the step (1) is 8-12.

Preferably, the feed position of the crude aldehyde in the step (1) is 2 to 3 theoretical plates from top to bottom in the lightness-removing column.

Preferably, the maaldehyde in the step (1) is crude furfural which is deacidified by water washing or alkali washing.

Preferably, the temperature of the top of the lightness-removing column in the step (1) is 30-70 ℃, and the pressure of the top of the lightness-removing column is 3-25 kPa.

Preferably, the mass of the overhead product of the light component removal tower in the step (1) is 0.8-1.2 times of the feeding amount of the light component removal tower; and condensing and separating distillate at the tower top in sequence to obtain a water phase and an oil phase, extracting the water phase into a water-aldehyde tank, and completely refluxing the oil phase into the light component removal tower.

Preferably, the theoretical plate number of the refining tower in the step (2) is 26-34, and the reflux ratio of the refining tower is 1.5-2.5.

Preferably, the feeding position of the first-stage material in the step (2) is 14 th to 24 th theoretical plates from top to bottom in the refining tower.

Preferably, the temperature of the top of the refining tower in the step (2) is 75-115 ℃, and the pressure of the top of the refining tower is 3-25 kPa.

When biomass hydrolysis is adopted to prepare furfural, furfural obtained by hydrolysis is discharged from a hydrolysis reactor through steam stripping, and deacidification is carried out through primary distillation, water washing or alkali washing after condensation, wherein the furfural content in the obtained crude furfural (crude aldehyde) is between 90 and 95 percent, and most of the rest is water, and light components such as methanol, acetic acid and the like and heavy components such as 2-acetylfuran, 5-methylfurfural and the like are also contained. Because the content of light components such as methanol and the like in the crude aldehyde is low, the additional value is low, and the recovery does not have economic value, the invention does not consider the recovery and the utilization of the light components, but removes the light components and water by a light component removal tower.

The invention provides a furfural refining method using water-washed or alkali-washed deacidified crude aldehyde as a raw material, which comprises the steps of firstly carrying out primary rectification by using a light component removal tower to remove light components such as methanol, water and acetic acid contained in the crude aldehyde, and then carrying out secondary rectification by using a refining tower to remove heavy components such as 2-acetylfuran and 5-methylfurfural. Compared with a single-tower refining process, the method has the advantages that double-tower continuous rectification is adopted, the processing capacity is improved, the product stability is more controllable, light components and heavy components can be completely removed by controlling the theoretical plate numbers, reflux ratios and feeding positions of the light component removal tower and the refining tower, and finally a high-purity high-quality furfural product is obtained. The results of the embodiments show that the furfural content in the high-quality furfural product obtained by the method for refining furfural provided by the invention can reach 99.99%, the content of light components such as methanol and water is lower than 0.01%, and the product quality is superior to the national standard of "industrial furfural GB/T1926.1-2009".

Drawings

FIG. 1 is a process flow diagram of a furfural purification method in an embodiment of the present invention; in the figure, 1 is a crude aldehyde tank, 2 is a crude aldehyde feed pump, 3 is a lightness-removing tower, 4 is a lightness-removing tower condenser, 5 is a lightness-removing tower reflux buffer tank, 6 is a knockout, 7 is a lightness-removing tower reboiler, 8 is a water aldehyde tank, 9 is a refining tower, 10 is a refining tower condenser, 11 is a refining tower reflux buffer tank, 12 is a refining tower reflux ratio controller, 13 is a finished product tank, 14 is a refining tower reboiler, and 15 is an aldehyde mud tank.

Detailed Description

The invention provides a furfural refining method, which comprises the following steps:

(1) performing primary rectification on the wool aldehyde by using a light component removal tower, and then extracting a primary material from a tower kettle of the light component removal tower;

the number of theoretical plates of the light component removal tower is 5-14;

the feeding position of the crude aldehyde is the 1 st to 5 th theoretical tower plates from top to bottom in the light component removal tower;

(2) performing secondary rectification on the primary material obtained in the step (1) by using a refining tower, and then extracting at the top of the refining tower to obtain a finished product furfural;

the theoretical plate number of the refining tower is 21-35, and the reflux ratio of the refining tower is 1-3;

the feeding position of the first-stage material is 12 th to 25 th theoretical plates from top to bottom in the refining tower.

The method comprises the steps of performing primary rectification on crude aldehyde by using a light component removal tower, and then extracting a primary material from a tower kettle of the light component removal tower.

In the present invention, the lightness-removing column is preferably a tray column or a packed column; when the light component removal tower is a plate tower, the efficiency of the plate tower is preferably 50-75%; when the light component removal tower is a packed tower, the equal plate height of the packing of the packed tower is preferably 0.3-1.0 m. In the present invention, the number of theoretical plates of the lightness-removing column is 5 to 14, more preferably 8 to 12. In the present invention, the overhead temperature of the lightness-removing column is preferably from 30 to 70 ℃ and more preferably from 40 to 65 ℃. In the present invention, the overhead pressure of the lightness-removing column is preferably 3 to 25kPa, more preferably 5 to 20 kPa. The invention controls the theoretical plate number, the tower top temperature and the tower top pressure of the light component removal tower within the ranges, and is beneficial to removing light components such as methanol, water and acetic acid contained in the crude aldehyde as far as possible, thereby reducing the light component content in the finally obtained furfural product and further improving the quality of the furfural product.

In the present invention, the method for preparing the aldehyde preferably comprises the steps of:

(a) carrying out atmospheric distillation on a furfural stock solution from a hydrolysis kettle by using a primary distillation tower, and then extracting at the top of the primary distillation tower to obtain an aldehyde-water azeotrope; introducing the tower kettle wastewater of the primary distillation tower into a wastewater treatment system;

(b) condensing and separating the aldehyde-water azeotrope obtained in the step (a) in sequence to obtain a water phase and an oil phase; refluxing the aqueous phase to a preliminary distillation column;

(c) and (c) washing the oil phase obtained in the step (b) by using a washing tower to obtain crude furfural, namely, crude aldehyde.

According to the invention, the primary distillation tower is preferably used for carrying out atmospheric distillation on the furfural stock solution from the hydrolysis kettle, and then the aldehyde-water azeotrope is obtained at the top of the primary distillation tower.

The preliminary distillation column of the present invention is not particularly limited, and may be any one using a device known in the art. The invention has no special limit on the temperature of the atmospheric distillation and can effectively extract and obtain the aldehyde-water azeotrope.

After obtaining the aldehyde-water azeotrope, the present invention preferably sequentially condenses and separates the aldehyde-water azeotrope to obtain an aqueous phase and an oil phase.

The invention has no special limitation on the operation of condensation and liquid separation, and can realize effective separation of the water phase and the oil phase.

After the aqueous phase is obtained, the aqueous phase is preferably refluxed to the preliminary distillation column in the present invention.

After the oil phase is obtained, the invention preferably utilizes a water washing tower to wash the oil phase to obtain the wool aldehyde.

The water washing tower is not particularly limited in the invention, and equipment known in the field can be adopted. The operation of the water washing is not particularly limited, and most of water-soluble impurities can be effectively removed by the water washing.

In the present invention, the wool aldehyde preferably includes, in mass fraction: 90-95% of furfural, 3-8% of water, 0.1-0.5% of acetic acid, 0.2-1% of methanol, 0.1-0.3% of 2-acetylfuran and 0.3-0.8% of 5-methylfurfural.

In the present invention, the crude aldehyde is fed at the 1 st to 5 th theoretical plates, more preferably at the 2 nd to 3 rd theoretical plates from the top in the lightness-removing column. The invention controls the feed position of the crude aldehyde in the range, and synergistically controls the number of theoretical plates, the pressure at the top of the tower, the temperature at the top of the tower and the reflux ratio of the lightness-removing tower in the range, thereby being beneficial to removing light components such as methanol, water, acetic acid and the like contained in the crude aldehyde as far as possible, reducing the content of the light components of the finally obtained furfural product and further improving the quality of the furfural product.

In the present invention, the primary rectification is preferably carried out under negative pressure.

In the present invention, the mass of the overhead of the lightness-removing column is preferably from 0.8 to 1.2 times, more preferably from 0.9 to 1 times, the feed amount to the lightness-removing column. The invention controls the quality of the distillate at the top of the light component removal tower in the range, which is beneficial to removing light component impurities such as methanol, water, acetic acid and the like in the crude aldehyde as far as possible.

After the first-stage rectification is finished, preferably, the distillate at the top of the tower is extracted, and then is sequentially condensed and separated to obtain a water phase and an oil phase, wherein the water phase is extracted into a water-aldehyde tank, and the oil phase is totally refluxed into a light component removal tower.

The present invention is not particularly limited to such condensation and may be carried out in a manner well known in the art. In the present invention, the pressure of the liquid separation is preferably 3 to 25kPa, more preferably 5 to 20kPa, and the temperature of the liquid separation is preferably 20 to 30 ℃, more preferably 23 to 26 ℃. The invention controls the pressure and temperature of the liquid separation within the above range, which is beneficial to the full separation of oil phase and water phase.

In the present invention, the aqueous phase preferably comprises water and small amounts of methanol, acetic acid light components. The invention is not particularly limited with respect to the type of water-aldehyde tank, and storage tanks known to those skilled in the art may be used.

In the present invention, the oil phase preferably comprises furfural. In the present invention, the oil phase preferably enters the lightness-removing column by refluxing from the top of the lightness-removing column.

In the present invention, the primary feed preferably comprises furfural, 2-acetylfuran and 5-methylfurfural.

After the primary material is obtained, the invention utilizes a refining tower to carry out secondary rectification on the primary material, and then the furfural product is obtained by extraction at the top of the refining tower.

In the present invention, the refining column is preferably a plate column or a packed column; when the refining tower is a plate tower, the plate efficiency of the plate tower is preferably 50-80%; when the refining tower is a packed tower, the equal plate height of the packing of the packed tower is preferably 0.3-1.0 m. In the present invention, the number of theoretical plates of the rectifying column is 21 to 35, more preferably 26 to 34. In the present invention, the feed position of the primary material is 12 th to 25 th theoretical plates from top to bottom in the refining column, and more preferably 14 th to 24 th theoretical plates. In the present invention, the reflux ratio of the refining column is 1 to 3, more preferably 1.5 to 2.5. In the present invention, the top temperature of the refining column is preferably 75 to 115 ℃, more preferably 80 to 110 ℃. In the present invention, the pressure at the top of the refining column is preferably 3 to 25kPa, more preferably 5 to 20 kPa. The invention controls the number of tower plates of the refining tower, the feeding position, the reflux ratio, the pressure and the temperature at the top of the tower within the ranges, and is beneficial to removing the 2-acetylfuran, the 5-methylfurfural and other heavy components contained in the first-grade material as far as possible, thereby reducing the content of the heavy components in the finally obtained furfural product and further improving the quality of the furfural product.

In the invention, the secondary rectification is preferably carried out under the condition of negative pressure, the negative pressure can reduce the temperature in the tower so as to reduce the reactions of coking, resinification and the like of the furfural, but the pressure cannot be too low, otherwise, the operation cost is increased.

In the secondary rectification process, the invention preferably partially reflows the finished furfural into the refining column. In the invention, the finished furfural partially flows back to the refining tower through the top of the refining tower. In the invention, the reflux amount and the extraction amount of the finished product furfural are determined by the material balance and the reflux ratio of the secondary rectification together, namely the material balance V of the rectification section is L + D, and the reflux ratio R is L/D, wherein V is the distillation amount of the total secondary rectification, L is the reflux amount, and D is the extraction amount.

In the secondary rectification process, the furfural mixed liquid containing a large amount of heavy component impurities, which is extracted from the tower kettle of the refining tower, is preferably sent to the aldehyde mud tank.

The present invention is not particularly limited in the type of the aldehyde mud tank, and an aldehyde mud tank well known to those skilled in the art may be used.

The method for refining furfural provided by the invention comprises the steps of firstly utilizing a light component removal tower to carry out primary rectification to remove light components such as methanol, water and acetic acid contained in the crude aldehyde, then utilizing a refining tower to carry out secondary rectification to remove heavy components such as 2-acetylfuran and 5-methylfurfural, adopting double-tower continuous rectification to improve the processing capacity and control the product stability, and completely removing the light components and the heavy components by controlling the tower plate number, reflux ratio, feeding position and other parameters of the light component removal tower and the refining tower to finally obtain a high-purity high-quality furfural product.

The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. 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

Fig. 1 is a process flow diagram of a furfural refining method in an embodiment, in which crude aldehyde in a crude aldehyde tank 1 is fed as a feed material into a lightness-removing column 3 through a crude aldehyde feed pump 2 at normal temperature and normal pressure to perform primary rectification, a still liquid in the lightness-removing column 3 is heated and vaporized by a lightness-removing column reboiler 7, a mass transfer is continuously performed between an ascending gas phase and a descending liquid phase, light components in the liquid phase are almost all transferred to the gas phase, a distillate at the top of the lightness-removing column 3 is condensed by a lightness-removing column condenser 4 and then enters a lightness-removing column buffer tank 5 and then enters a liquid separator 6, an oil phase obtained after liquid separation enters the lightness-removing column 3 from the top of the lightness-removing column 3 to reflux, and a water phase obtained after liquid separation is collected into a water aldehyde tank 8. The method comprises the steps of extracting a first-grade material from a tower kettle of a light component removal tower 3, feeding the first-grade material into a refining tower 9 for secondary rectification, heating and vaporizing a kettle liquid of the refining tower 9 through a light component removal tower reboiler 14, continuously transferring materials between a gas phase rising from the tower kettle and a liquid phase falling from the tower top, continuously removing heavy components in the gas phase, finally condensing a distillate at the tower top of the refining tower 9 through a refining tower condenser 10 to obtain a finished product furfural, feeding the finished product furfural into a refining tower reflux buffer tank 11, controlling a certain reflux ratio by using a refining tower reflux ratio controller 12 to reflux part of the finished product furfural into the refining tower 9, extracting the rest part of the finished product furfural, feeding the furfural mixed liquid containing a large amount of heavy component impurities, which is extracted from the tower kettle of the refining tower 9 into a finished product tank 13, and feeding the furfural mixed liquid containing a large amount of heavy component impurities into an aldehyde mud tank 15.

(1) Performing primary rectification on the wool aldehyde by using a light component removal tower, and then extracting a primary material from a tower kettle of the light component removal tower;

the theoretical plate number of the light component removal tower is 7, a plate type tower is adopted, the plate efficiency is 50%, and the actual plate number is 14;

according to the mass fraction, the maldehyde comprises 93.15% of furfural, 5% of water, 0.47% of acetic acid, 0.5% of methanol, 0.2% of 2-acetylfuran and 0.68% of 5-methylfurfural;

the feeding positions of the crude aldehyde are a theoretical plate 2 and an actual plate 4 counted from top to bottom in the light component removal tower;

the feed temperature of the wool aldehyde is 25 ℃;

the temperature of the top of the light component removal tower is 40 ℃, and the pressure of the top of the light component removal tower is 5 kpa;

after being extracted, the distillate at the top of the light component removal tower is condensed by a condenser and then enters a liquid separator, and a water phase and an oil phase are obtained through liquid separation; extracting the water phase into a water-aldehyde tank, and refluxing the oil phase into a light component removal tower;

in the first-stage material, the content of furfural is 98.93%, and the content of water is lower than 0.01%;

(2) performing secondary rectification on the primary material obtained in the step (1) by using a refining tower, and then extracting at the top of the refining tower to obtain a finished product furfural;

the theoretical plate number of the refining tower is 28, a plate type tower is adopted, the plate efficiency is 80%, the actual plate number is 35, and the reflux ratio of the refining tower is 2.5;

the feeding position of the first-stage material is 15 th theoretical plate and 19 th actual plate from top to bottom in the refining tower.

The top temperature of the refining tower is 76 ℃, and the top pressure of the refining tower is 5 kpa;

condensing the tower top distillate of the refining tower through a condenser to obtain a finished product furfural, refluxing part of the finished product furfural to the refining tower, and extracting the rest of the finished product furfural and sending the extracted finished product furfural into a finished product tank;

in the finished product of furfural, the content of furfural is 99.94%, the content of water is lower than 0.01%, the content of 2-acetylfuran is 0.03%, and the content of 5-methylfurfural is 0.02% (the content of water is determined by a Karl Fischer method, and other components are determined by chromatography).

Example 2

Furfural refining method

(1) Performing primary rectification on the wool aldehyde by using a light component removal tower, and then extracting a primary material from a tower kettle of the light component removal tower;

the theoretical plate number of the light component removal tower is 12, a plate type tower is adopted, the plate efficiency is 75%, and the actual plate number is 16;

according to mass fraction, the maaldehyde comprises 94.65% of furfural, 3.83% of water, 0.25% of acetic acid, 0.55% of methanol, 0.2% of 2-acetylfuran and 0.52% of 5-methylfurfural;

the feeding positions of the crude aldehyde are a theoretical plate 3 and an actual plate 4 from top to bottom in the light component removal tower;

the feed temperature of the wool aldehyde is 25 ℃;

the temperature of the top of the light component removal tower is 52 ℃, and the pressure of the top of the light component removal tower is 10 kpa;

after being extracted, the distillate at the top of the light component removal tower is condensed by a condenser and then enters a liquid separator, and a water phase and an oil phase are obtained through liquid separation; extracting the water phase into a water-aldehyde tank, and refluxing the oil phase into a light component removal tower;

in the first-stage material, the content of furfural is 99.05%, and the content of water is lower than 0.01%;

(2) performing secondary rectification on the primary material obtained in the step (1) by using a refining tower, and then extracting at the top of the refining tower to obtain a finished product furfural;

the theoretical plate number of the refining tower is 30, a plate type tower is adopted, the plate efficiency is 50%, the actual plate number is 60, and the reflux ratio of the refining tower is 2.0;

the feeding position of the first-stage material is an 18 th theoretical plate and a 36 th actual plate from top to bottom in the refining tower.

The top temperature of the refining tower is 92 ℃, and the top pressure of the refining tower is 10 kpa;

condensing the tower top distillate of the refining tower through a condenser to obtain a finished product furfural, refluxing part of the finished product furfural to the refining tower, and extracting the rest of the finished product furfural and sending the extracted finished product furfural into a finished product tank;

in the finished product of furfural, the content of furfural is 99.99%, the content of water is lower than 0.01%, and trace amounts of 2-acetylfuran and 5-methylfurfural (the content of water is determined by a Karl Fischer method, and other components are determined by chromatography) are obtained.

Example 3

Furfural refining method

(1) Performing primary rectification on the wool aldehyde by using a light component removal tower, and then extracting a primary material from a tower kettle of the light component removal tower;

the number of theoretical plates of the light component removal tower is 13, a packed tower is adopted, the equal plate height of the packing is 1m, and the actual packing height is 13 m;

according to the mass fraction, the maldehyde comprises 92.25% of furfural, 6% of water, 0.3% of acetic acid, 0.5% of methanol, 0.3% of 2-acetylfuran and 0.65% of 5-methylfurfural;

the feeding position of the crude aldehyde is the 4 th theoretical plate from top to bottom in the light component removal tower, and the actual feeding position is the 4 th m position from top to bottom of the filler;

the feed temperature of the wool aldehyde is 25 ℃;

the temperature of the top of the light component removal tower is 65 ℃, and the pressure of the top of the light component removal tower is 20 kpa;

after being extracted, the distillate at the top of the light component removal tower is condensed by a condenser and then enters a liquid separator, and a water phase and an oil phase are obtained through liquid separation; the pressure of the liquid separator is 20kpa, and the temperature of the liquid separator is 25 ℃; extracting the water phase into a water-aldehyde tank, and refluxing the oil phase into a light component removal tower;

in the first-stage material, the content of furfural is 99.04%, and the content of water is lower than 0.01%;

(2) performing secondary rectification on the primary material obtained in the step (1) by using a refining tower, and then extracting at the top of the refining tower to obtain a finished product furfural;

the theoretical plate number of the refining tower is 32, a packed tower is adopted, the equal plate height of the packing is 0.6m, the actual packing height is 19.2m, and the reflux ratio of the refining tower is 1.2;

the feeding position of the first-stage material is the 20 th theoretical plate from top to bottom in the refining tower, and the actual feeding position is the 12 th position from top to bottom of the filler.

The top temperature of the refining tower is 110 ℃, and the top pressure of the refining tower is 20 kpa;

condensing the tower top distillate of the refining tower through a condenser to obtain a finished product furfural, refluxing part of the finished product furfural to the refining tower, and extracting the rest of the finished product furfural and sending the extracted finished product furfural into a finished product tank;

in the finished product of furfural, the content of furfural is 99.91%, the content of water is lower than 0.01%, 2-acetylfuran is 0.06%, and 5-methylfurfural is 0.01% (the water content is determined by a Karl Fischer method, and other components are determined by chromatography).

TABLE 1 Furfural content and Water content (mass fraction) in finished Furfural obtained in examples 1 to 3

Examples	1	2	3
				Furfural (%, mass fraction)	99.94	99.99	99.91
Water (%, mass fraction)	Less than 0.01 percent	Less than 0.01 percent	Less than 0.01 percent

As can be seen from the examples and table 1, the furfural obtained by the method for refining furfural provided by the present invention contains 99.99% of furfural by mass, less than 0.01% of water, and almost no heavy components (2-acetylfuran, 5-methylfurfural, etc.), and the product quality meets the national standard of "industrial furfural GB/T1926.1-2009"), which is much higher than the prior art (the furfural product in the prior art contains 0.04% of water by mass, 0.1% -0.2% of 2-acetylfuran, and 0.3% -0.8% of 5-methylfurfural by mass). The invention adopts double-tower continuous rectification, improves the processing capacity, has more controllable product stability, obviously reduces the water content in the furfural product by controlling the tower plate number, the reflux ratio and the feeding position of the light component removal tower and the refining tower, and completely removes light components and heavy components, thereby finally obtaining the high-purity high-quality furfural product.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.