阅读说明：本技术 一种脱除四氢呋喃中微量杂质的装置及方法 (Device and method for removing trace impurities in tetrahydrofuran ) 是由 王世忠 吴高胜 许保云 艾波 包春凤 刘陈真 李瑜哲 翟金国 于 2021-01-30 设计创作，主要内容包括：本发明涉及一种脱除四氢呋喃中微量杂质的装置及方法,该装置包括：闭路循环吸附系统：其包括依次连接并构成循环的原料储罐和分子筛吸附床；与闭路循环吸附系统相连接的精密精馏系统：其包括塔釜、塔体、塔顶冷凝器、塔顶回流罐、轻组分储罐和产品罐,所述的塔釜内设有再沸器,所述的塔体内装填有填料,且在填料上方还安装有液体分布器,所述的塔顶冷凝器的两端分别连接所述塔体的顶部气相出口和塔顶回流罐,所述塔顶回流罐的出口还分别返回连接所述塔体、以及轻组分储罐和产品罐。与现有技术相比,本发明可实现将四氢呋喃中微量乙醇杂质浓度降低至1ppm以下,将四氢呋喃的纯度精制到99.9％wt以上。(The invention relates to a device and a method for removing trace impurities in tetrahydrofuran, wherein the device comprises the following components: closed cycle adsorption system: the device comprises a raw material storage tank and a molecular sieve adsorption bed which are sequentially connected and form a cycle; a precision rectification system connected with the closed cycle adsorption system: it includes tower cauldron, tower body, top of the tower condenser, top of the tower backward flow jar, light component storage tank and product jar, the tower cauldron in be equipped with the reboiler, the tower body in be filled with filler, and still install liquid distributor above filler, the top of the tower condenser both ends connect respectively the top gas phase export and the top of the tower backward flow jar of tower body, the export of top of the tower backward flow jar still returns respectively to be connected tower body and light component storage tank and product jar. Compared with the prior art, the method can reduce the concentration of trace ethanol impurities in the tetrahydrofuran to below 1ppm and refine the purity of the tetrahydrofuran to above 99.9 wt%.)

1. A device for removing trace impurities in tetrahydrofuran is characterized by comprising:

closed cycle adsorption system: the device comprises a raw material storage tank and a molecular sieve adsorption bed which are sequentially connected and form a cycle;

a precision rectification system connected with the closed cycle adsorption system: it includes tower cauldron, tower body, top of the tower condenser, top of the tower backward flow jar, light component storage tank and product jar, the tower cauldron in be equipped with the reboiler, the tower body in be filled with filler, and still install liquid distributor above filler, the top of the tower condenser both ends connect respectively the top gas phase export and the top of the tower backward flow jar of tower body, the export of top of the tower backward flow jar still returns respectively to be connected tower body and light component storage tank and product jar.

2. The device for removing trace impurities in tetrahydrofuran according to claim 1, wherein a liquid delivery pump is further disposed between the raw material storage tank and the molecular sieve adsorbent bed, and an outlet of the liquid delivery pump is further connected to the tower body.

3. The apparatus according to claim 1, wherein the operating pressure of the molecular sieve adsorbent bed is atmospheric pressure or micro-positive pressure.

4. The device for removing trace impurities in tetrahydrofuran according to claim 1, wherein the operating pressure of the tower body is 1-1.3 atm absolute, and the reflux ratio is 1-20: 1.

5. The apparatus for removing trace impurities from tetrahydrofuran according to claim 1, wherein said packing has a theoretical plate number of 40 to 75.

6. The apparatus as claimed in claim 1, wherein the distribution point density of the liquid distributor in the column body is 300-800 particles/m²。

7. The apparatus according to claim 1, wherein an overhead liquid reflux valve, a light component feed valve and a product feed valve are further disposed between the overhead reflux tank and the column body, the light component storage tank and the product tank, respectively.

8. A method for removing trace impurities from tetrahydrofuran, which is carried out by the apparatus according to any one of claims 1 to 7, comprising the steps of:

(1) sending a tetrahydrofuran solution to be treated into a closed cycle adsorption system, enabling the tetrahydrofuran solution to circularly flow between a raw material storage tank and a molecular sieve adsorption bed, and when the content of ethanol in the tetrahydrofuran solution is lower than 1ppm, conveying the tetrahydrofuran solution to a precision rectification system;

(2) tetrahydrofuran solution discharged from the closed cycle adsorption system is heated and vaporized by a reboiler in a tower kettle to form ascending steam, the ascending steam carries out gas-liquid mass transfer and heat transfer on the surface of a filler, then the ascending steam is condensed and liquefied in a tower top condenser, after the condensed liquid is distributed by a tower top reflux tank, one part of the condensed liquid flows back to a tower body, and the other part of the condensed liquid is extracted to a light component storage tank or a product tank.

9. The method for removing trace impurities from tetrahydrofuran according to claim 8, wherein when the temperature of the uppermost position of the packing is lower than the boiling temperature of tetrahydrofuran at the operating pressure of the column, the overhead distillate is controlled to be discharged to the light component storage tank;

when the temperature of the uppermost position of the filler is equal to the boiling temperature of tetrahydrofuran under the operation pressure of the tower body, controlling the fraction extracted from the tower top to be discharged to a product tank;

when the temperature of the uppermost position of the filler is higher than the boiling temperature of tetrahydrofuran under the operation pressure of the tower body, the extraction at the top of the tower is stopped, and the tetrahydrofuran solution in the tower kettle is discharged.

10. The method as claimed in claim 8, wherein the tetrahydrofuran solution to be treated contains ethanol in an amount of 1-20000ppm, trace impurities in an amount of 0-5000ppm, and when trace impurities are contained, the boiling point of trace impurities is different from that of tetrahydrofuran by more than 5 ℃.

Technical Field

The invention belongs to the technical field of chemical separation, and relates to a device and a method for removing trace impurities in tetrahydrofuran.

Background

Tetrahydrofuran is a class of heterocyclic organic compounds. It is one of the most polar ethers and is used as a moderately polar solvent in chemical reactions and extractions. It is a colorless transparent liquid. Has an ether-like odor. The relative density was 0.89. Molecular weight 72.11. Melting Point-108.5 ℃. The boiling point is 66 ℃.

Tetrahydrofuran is often used as a solvent in industry, wherein tetrahydrofuran can be used as a recycling solvent in the process of preparing polyolefin catalysts, but trace ethanol and other trace impurities can be generated due to certain reaction mechanisms in the preparation process of the catalysts, and the trace impurities can have important influence on the quality of the catalysts. Therefore, the tetrahydrofuran in the preparation process of the catalyst needs to be refined, recovered and removed of trace impurities for recycling. Tetrahydrofuran and ethanol are azeotropic systems, belong to the lowest azeotrope, and can not meet the requirements by adopting a common separation process. The available technological processes in reported data include pressure swing rectification, azeotropic rectification, extractive rectification, membrane rectification, etc.

The patent (CN103394209B) discloses a method for separating ethanol and tetrahydrofuran azeotrope system by low-pressure and high-pressure double-tower distillation, which utilizes the difference of azeotropic compositions of tetrahydrofuran and ethanol under different pressures to separate the azeotrope system, and the purity of tetrahydrofuran product obtained by the process is 99.73-99.95%.

The patent (CN109678820A) discloses a method for separating tetrahydrofuran-ethanol-water mixture by complete thermal coupling extractive distillation, dimethyl sulfoxide is used as an extracting agent, 99.85% -99.9% tetrahydrofuran is obtained by utilizing the principle of physical properties of different substances, and meanwhile, a thermal coupling process is adopted in the process to reduce energy consumption.

In the above patent, it is difficult to apply to more multi-component systems and trace impurity systems only for binary or ternary systems, and it is difficult to ensure that the ethanol content in the tetrahydrofuran solution obtained by pressure swing distillation is below 1ppm, and at the same time, the tetrahydrofuran solution obtained by extractive distillation needs to be added with additional solvent.

Disclosure of Invention

The invention aims to provide a device and a method for removing trace impurities in tetrahydrofuran, which are used for reducing the concentration of trace ethanol impurities in the tetrahydrofuran to below 1ppm and refining the purity of the tetrahydrofuran to above 99.9 wt%.

The purpose of the invention can be realized by the following technical scheme:

one of the technical schemes of the invention provides a device for removing trace impurities in tetrahydrofuran, which comprises:

closed cycle adsorption system: the device comprises a raw material storage tank and a molecular sieve adsorption bed which are sequentially connected and form a cycle;

a precision rectification system connected with the closed cycle adsorption system: it includes tower cauldron, tower body, top of the tower condenser, top of the tower backward flow jar, light component storage tank and product jar, the tower cauldron in be equipped with the reboiler, the tower body in be filled with filler, and still install liquid distributor above filler, the top of the tower condenser both ends connect respectively the top gas phase export and the top of the tower backward flow jar of tower body, the export of top of the tower backward flow jar still returns respectively to be connected tower body and light component storage tank and product jar.

Further, a liquid delivery pump is further arranged between the raw material storage tank and the molecular sieve adsorption bed, and an outlet of the liquid delivery pump is further connected with the tower body.

Further, the operating pressure of the molecular sieve adsorption bed is normal pressure or micro-positive pressure.

Further, the operation pressure of the tower body is 1-1.3 atm absolute pressure, and the reflux ratio is 1-20: 1.

Further, the packing has a theoretical plate number of 40 to 75 pieces.

Further, the distribution point density of the liquid distributor in the tower body is 300-²。

Further, a tower top liquid reflux valve, a light component feeding valve and a product feeding valve are further arranged between the tower top reflux tank and the tower body, between the tower top reflux tank and the light component storage tank and between the tower top reflux tank and the product tank.

The second technical scheme of the invention provides a method for removing trace impurities in tetrahydrofuran, which is implemented by adopting the device and comprises the following steps:

(1) sending a tetrahydrofuran solution to be treated into a closed cycle adsorption system, enabling the tetrahydrofuran solution to circularly flow between a raw material storage tank and a molecular sieve adsorption bed, and when the content of ethanol in the tetrahydrofuran solution is lower than 1ppm, conveying the tetrahydrofuran solution to a precision rectification system;

(2) tetrahydrofuran solution discharged from the closed cycle adsorption system is heated and vaporized by a reboiler in a tower kettle to form ascending steam, the ascending steam carries out gas-liquid mass transfer and heat transfer on the surface of a filler, then the ascending steam is condensed and liquefied in a tower top condenser, after the condensed liquid is distributed by a tower top reflux tank, one part of the condensed liquid flows back to a tower body, and the other part of the condensed liquid is extracted to a light component storage tank or a product tank.

Further, when the temperature of the uppermost position of the filler is lower than the boiling temperature of tetrahydrofuran under the tower body operation pressure, controlling the fraction extracted from the tower top to be discharged to a light component storage tank;

when the temperature of the uppermost position of the filler is equal to the boiling temperature of tetrahydrofuran under the operation pressure of the tower body, controlling the fraction extracted from the tower top to be discharged to a product tank;

when the temperature of the uppermost position of the filler is higher than the boiling temperature of tetrahydrofuran under the operation pressure of the tower body, the extraction at the top of the tower is stopped, and the tetrahydrofuran solution in the tower kettle is discharged.

Further, the tetrahydrofuran solution to be treated has an ethanol content of 1 to 20000ppm and a trace impurity content of 0 to 5000ppm, and when the trace impurity is contained, the boiling point of the trace impurity is different from that of tetrahydrofuran by more than 5 ℃.

Compared with the prior art, the invention has the following advantages:

(1) the method has the advantages of simple process, convenient operation and stable and reliable system, and can reduce the concentration of trace ethanol impurities in the tetrahydrofuran to below 1ppm and refine the purity of the tetrahydrofuran to above 99.9 percent by weight;

(2) compared with pressure swing rectification, the process system has lower pressure operation and does not relate to a high-pressure operation system;

(3) compared with the extraction and rectification, no additional substance is added in the process, so that the risk of secondary pollution of the tetrahydrofuran product is reduced.

Drawings

FIG. 1 is a schematic structural view of the present invention;

the notation in the figure is:

1-a raw material storage tank; 2-a liquid delivery pump; 3-a molecular sieve adsorption bed; 4-valve one; 5, a valve II; 6-a liquid distributor; 7-a tower body; 8-a filler; 9-tower kettle; 10-a reboiler; 11-heating steam; 12-tower kettle condensation water; 13-a blow-down valve; 14-overhead condenser; 15-overhead reflux drum; 16-overhead liquid reflux valve; 17-overhead take-off valve; 18-light component feed valve; 19-product feed valve; 20-a light component storage tank; 21-product tank.

Detailed Description

The invention is described in detail below with reference to the figures and specific embodiments. The present embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation manner and a specific operation process are given, but the scope of the present invention is not limited to the following embodiments.

In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

The following first describes the apparatus for removing trace impurities in tetrahydrofuran according to the present invention:

the device for removing trace impurities in tetrahydrofuran provided by the invention has a structure shown in figure 1, and comprises:

closed cycle adsorption system: the device comprises a raw material storage tank 1 and a molecular sieve adsorption bed 3 which are sequentially connected and form a cycle;

a precision rectification system connected with the closed cycle adsorption system: it includes tower cauldron 9, tower body 7, top of the tower condenser 14, top of the tower reflux drum 15, light component storage tank 20 and product jar 21, tower cauldron 9 in be equipped with reboiler 10, tower body 7 in be filled with filler 8, and still install liquid distributor 6 above filler 8, top of the tower condenser 14 both ends connect respectively the top gas phase outlet and the top of the tower reflux drum 15 of tower body 7, the export of top of the tower reflux drum 15 still returns respectively and connects tower body 7 and light component storage tank 20 and product jar 21.

In some embodiments, a liquid delivery pump 2 is further disposed between the raw material storage tank 1 and the molecular sieve adsorption bed 3, and an outlet of the liquid delivery pump 2 is further connected to the tower body 7. In the present invention, the molecular sieve adsorbent bed 3 may be provided in one or a plurality of beds connected in series according to the treatment requirements.

In some embodiments, the operating pressure of the molecular sieve adsorbent bed 3 is atmospheric pressure or slightly positive pressure, and the optimal operating pressure is 1.05bar absolute. The operating pressure of the molecular sieve adsorption bed 3 and the rectifying tower 7 is preferably micro-positive pressure operation, the main purpose of the micro-positive pressure operation is to remove the influence of micro-leakage on the process caused by flange connection between equipment, between equipment and pipelines, and between equipment and instruments, when the pressure in the system is kept to be micro-positive pressure, the pressure at the position of a leakage point possibly existing in the system is outward from the inside of the system, and the system is guaranteed not to be interfered by the external environment.

In some embodiments, the tower 7 is operated at a pressure of 1 to 1.3atm absolute, preferably 1.1 to 1.2bar absolute, with a reflux ratio of 1 to 20:1, and an optimal reflux ratio of 7:1 to 12: 1.

In some embodiments, the packing 8 has a theoretical plate number of 40 to 75, and most preferably 55 to 60, and the actual packing height of the packing 8 is preferably not more than 15 m.

In some embodiments, the liquid distributor 6 has a distribution point density of 300-²The optimal distribution point density is 450-²In addition, the number of the liquid distributors 6 is not preferably more than 7.

In some embodiments, an overhead liquid reflux valve 16, a lights feed valve 18, and a product feed valve 19 are also provided between the overhead reflux drum 15 and the column 7, lights storage tank 20, and product tank 21, respectively.

In some embodiments, a first valve 4 is disposed between the raw material storage tank 1 and the molecular sieve adsorption bed 3, and a second valve 5 is disposed between the closed cycle adsorption system and the precision rectification system, as shown in fig. 1.

The following description is continued for the method of removing trace impurities in tetrahydrofuran according to the present invention:

in some embodiments, the method for removing trace impurities in tetrahydrofuran by using the device comprises the following steps:

(1) sending a tetrahydrofuran solution to be treated into a closed cycle adsorption system, enabling the tetrahydrofuran solution to circularly flow between a raw material storage tank 1 and a molecular sieve adsorption bed 3, and when the content of ethanol in the tetrahydrofuran solution is lower than 1ppm, conveying the tetrahydrofuran solution to a precision rectification system;

(2) tetrahydrofuran solution discharged from the closed cycle adsorption system is heated and vaporized by heating steam 11 in a reboiler 10 in a tower kettle 9 to form rising steam, the rising steam carries out gas-liquid mass transfer and heat transfer on the surface of a filler 8, then the rising steam is condensed and liquefied in a tower top condenser 14, after being distributed by a tower top reflux tank 15, a part of the condensed liquid flows back to a tower body 7, and forms a layer of liquid film on the surface of the filler 8 to carry out mass transfer and heat transfer after passing through a liquid distributor 6, and the other part of the condensed liquid is extracted to a light component storage tank 20 or a product tank 21. Preferably, the tower bottom condensed water 12 formed after the heat transfer of the heating steam 11 in the reboiler 10 is discharged.

Specifically, when the temperature of the uppermost position of the filler 8 is lower than the boiling temperature of tetrahydrofuran under the operation pressure of the tower body 7, the fraction extracted from the tower top is controlled to be discharged to the light component storage tank 20;

when the temperature of the uppermost position of the filler 8 is equal to the boiling temperature of tetrahydrofuran under the operation pressure of the tower body 7, controlling the fraction extracted from the tower top to be discharged to the product tank 21;

when the temperature of the uppermost position of the filler 8 is higher than the boiling temperature of tetrahydrofuran under the operation pressure of the tower body 7, the extraction at the top of the tower is stopped, and the tetrahydrofuran solution in the tower kettle 9 is discharged through a drain valve 13.

Specifically, the ethanol content in the tetrahydrofuran solution to be treated is 1-20000ppm, the content of trace impurities is 0-5000ppm, and when the trace impurities are contained, the boiling point of the trace impurities is different from that of tetrahydrofuran by more than 5 ℃. And ensures that the content of ethanol in the tetrahydrofuran solution is reduced to below 1ppm after passing through the molecular sieve adsorption bed 3; after passing through a precise rectification system, the purity of the tetrahydrofuran reaches more than 99.9 percent by weight.

The above embodiments may be implemented individually, or in any combination of two or more.

The above embodiments will be described in more detail with reference to specific examples

Example 1:

the raw materials comprise: 0.79 wt% of ethanol, 0.23 wt% of light component, 98.94 wt% of tetrahydrofuran and 0.04 wt% of heavy component.

The bed layer of the molecular sieve adsorbent bed 3 was filled with 0.5L of a modified 5A molecular sieve purification agent, the adsorbent model was LQMS05, the operating pressure was 1.05bar (absolute), the molecular sieve packing amount: the raw material amount is 1:2 (volume ratio), a peristaltic pump is used as a liquid delivery pump 2, after 1h of cyclic adsorption, the raw material is analyzed by gas chromatography, wherein the ethanol content in the adsorbed raw material is lower than 1 ppm; introducing the adsorbed raw materials into an intermittent precise rectifying tower (namely a tower body 7) for refining tetrahydrofuran, wherein the operating parameters of the rectifying tower are as follows: the theoretical plate number is 55, the reflux ratio is 10:1, the operation pressure at the top of the tower is kept at 1.15bar, light components and products are extracted from the top of the tower in stages, and heavy components are extracted from a tower kettle 9.

Then, the operation flow shown in fig. 1 is adopted, which specifically includes the following steps:

(1) sending a tetrahydrofuran solution to be treated into a closed cycle adsorption system, enabling the tetrahydrofuran solution to circularly flow between a raw material storage tank 1 and a molecular sieve adsorption bed 3, and when the content of ethanol in the tetrahydrofuran solution is lower than 1ppm, conveying the tetrahydrofuran solution to a precision rectification system;

(2) tetrahydrofuran solution discharged from a closed cycle adsorption system is heated and vaporized by a reboiler 10 in a tower kettle 9 to form ascending steam, the ascending steam carries out gas-liquid mass transfer and heat transfer on the surface of a filler 8, then is condensed and liquefied in a tower top condenser 14, after the condensed liquid is distributed by a tower top reflux tank 15, one part of the condensed liquid flows back to a tower body 7, and forms a layer of liquid film on the surface of the filler 8 after passing through a liquid distributor 6 to carry out mass transfer and heat transfer, and the other part of the condensed liquid is extracted to a light component storage tank 20 or a product tank 21;

when the temperature of the uppermost position of the filler 8 is lower than the boiling temperature of tetrahydrofuran under the operation pressure of the tower body 7, controlling the fraction extracted from the tower top to be discharged to the light component storage tank 20;

when the temperature of the uppermost position of the filler 8 is equal to the boiling temperature of tetrahydrofuran under the operation pressure of the tower body 7, controlling the fraction extracted from the tower top to be discharged to the product tank 21;

when the temperature of the uppermost position of the filler 8 is higher than the boiling temperature of tetrahydrofuran under the operation pressure of the tower body 7, the extraction from the tower top is stopped, and the tetrahydrofuran solution in the tower kettle 9 is discharged.

The tetrahydrofuran content in the final product is 99.9 wt%, the ethanol content is lower than 1ppm, and the product yield is 86.61 wt%.

Example 2:

the raw materials comprise: 0.66 percent of ethanol, 0.35 percent of light component, 98.89 percent of tetrahydrofuran and 0.1 percent of heavy component.

Bed filling of molecular sieve adsorption bed 3 is 1.5m³Modified 5A molecular sieve purification agent, adsorbent model number LQMS05, operating pressure 1.05bar (absolute), molecular sieve packing: the raw material amount is 1:3 (volume ratio), a peristaltic pump is used as a liquid delivery pump 2, after circulating adsorption for 2 hours, the raw material is analyzed by gas chromatography, wherein the ethanol content in the adsorbed raw material is lower than 1 ppm; the adsorbed raw materials are refined by tetrahydrofuran through an intermittent precise rectifying tower (namely a tower body 7), and the operating parameters of the rectifying tower are as follows: the theoretical plate number is 60, the reflux ratio is 7:1, the operation pressure at the top of the tower is kept at 1.1bar, light components and products are extracted from the top of the tower in stages, heavy components are extracted from a tower kettle 9, and the specific treatment process can refer to the example 1.

Finally, under the above process conditions, the tetrahydrofuran content in the product obtained in this example is 99.96-99.99% wt, the ethanol content is less than 1ppm, and the product yield is maintained above 85% wt.

Comparative example 1:

compared with the embodiment 1, the method is mostly the same, and the step of molecular sieve cyclic adsorption is omitted, namely, the raw material is directly fed into a batch precision rectifying tower for refining.

The raw materials comprise: 99.45 percent of tetrahydrofuran, 560ppm of ethanol, 0.3 percent of light component and 0.194 percent of heavy component. The raw materials are directly separated in a rectifying tower (namely a tower body 7), and the operating parameters of the rectifying tower are as follows: the theoretical plate number is 60, the reflux ratio is 10:1, the operation pressure at the top of the tower is 1.15bar, the content of ethanol in the components extracted from the top of the tower is changed, the content of ethanol in the top of the tower is enriched to 1200-1500ppm in the total reflux stage, the ethanol is gradually extracted according to the operation parameters of the rectifying tower, the content of the ethanol at the top of the tower is gradually reduced, but the ethanol content is not changed when the ethanol content is reduced to 70-100ppm, namely the content of the ethanol cannot be reduced to below 1ppm by only adopting precise rectification through practical experimental research.

Comparative example 2:

compared with example 1, most of them are the same except that the process form of the molecular sieve adsorption bed 3 is changed to continuous operation.

The raw materials comprise: 99.45 percent of tetrahydrofuran, 560ppm of ethanol, 0.3 percent of light component and 0.194 percent of heavy component. The molecular sieve adsorption is designed according to a continuous process design, 3 molecular sieve adsorption beds and A, B, C molecular sieve adsorption beds are arranged in the designed adsorption process, in the actual process, the molecular sieve adsorption beds are used for two purposes, for example, raw materials firstly pass through the molecular sieve adsorption bed A and then pass through the molecular sieve adsorption bed B, the molecular sieve adsorption bed C is in a standby state, when the molecular sieve adsorption bed A is saturated, the material flow is changed to firstly pass through the molecular sieve adsorption bed B and then pass through the molecular sieve adsorption bed C, and the molecular sieve adsorption bed A is in an activated state.

Comparative example 3:

compared with the embodiment 2, the operation pressure of the molecular sieve adsorption bed 3 is changed to normal pressure, and the operation pressure of the rectifying tower 7 is changed to normal pressure operation.

The raw materials comprise: 0.66 percent of ethanol, 0.35 percent of light component, 98.89 percent of tetrahydrofuran and 0.1 percent of heavy component. Molecular sieve adsorption bed 3 is filled with 1.5m³Modified 5A molecular sieve purification agent, adsorbent model is LQMS05, operating pressure is normal pressure (communicated with atmosphere), molecular sieve filling amount: the raw material amount is 1:3 (volume ratio), the ethanol content of the raw material after adsorption is below 1ppm for most of time, but the adsorption solvent sampled at different times, wherein the ethanol content of individual solvent samples is 2-5ppm, and the operation of an adsorption section is not very stable; the raw material treated in the adsorption section passes through an intermittent precision rectifying tower (namely a tower)Body 7) was refined with tetrahydrofuran, operating parameters of the rectification column: the theoretical plates are 60, the reflux ratio is 7:1, the operation pressure at the top of the tower is kept at normal pressure (communicated with the atmosphere), and when the ethanol content in the raw material entering the intermittent precise rectifying tower is 5ppm, about 50% wt of the raw material is required to be extracted from the top of the tower, so that the ethanol content can be reduced to below 1 ppm.

The embodiments described above are described to facilitate an understanding and use of the invention by those skilled in the art. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make improvements and modifications within the scope of the present invention based on the disclosure of the present invention.