Method and device for refining tetrahydrofuran, a by-product of 1,4-butanediol dehydrogenation, by coupling a tower and a membrane

Abstract

The present invention discloses a device for refining tetrahydrofuran, a by-product of 1,4-butanediol dehydrogenation, by coupling a tower and a membrane, which comprises a membrane-coupled tower, a membrane module, a post-membrane tower and a tetrahydrofuran tower connected in sequence. The material from the tetrahydrofuran raw material storage tank enters the middle part of the membrane-coupled tower after being preheated by a preheater. The top of the membrane-coupled tower is divided into two pipelines. One pipeline is connected to the membrane module, and the other pipeline is connected to the shell side of a second reboiler. The outlet of the shell side of the second reboiler is connected to the upper part of the membrane-coupled tower. The upstream side of the membrane of the membrane module is connected to the middle part of the post-membrane tower. The light components at the top of the post-membrane tower enter the next-stage methanol distillation tower for distillation. The side line is connected to the reflux of the tetrahydrofuran to the membrane-coupled tower. The bottom of the tower is connected to the middle part of the tetrahydrofuran tower. The bottom of the post-membrane tower is also connected to the tube side of the second reboiler. The target product with a water content of ≤0.02% and a tetrahydrofuran content of ≥99.9% is obtained at the top of the tetrahydrofuran tower. The present invention also discloses a method for refining tetrahydrofuran, a by-product of 1,4-butanediol dehydrogenation, by coupling a tower and a membrane.

Description

Technical Field

[0001] The present invention belongs to the technical field of chemical production equipment, and particularly relates to a method and device for refining tetrahydrofuran, a by-product of 1,4-butanediol dehydrogenation, by coupling a tower and a membrane. Background Art

[0002] Tetrahydrofuran (THF), molecular formula: C4H8O, also known as 1,4-epoxybutane, is a heterocyclic organic compound belonging to ethers, with a boiling point of 66 °C. At low temperatures, THF is miscible with water. It is a colorless, low-viscosity transparent liquid with an odor similar to that of ether, and has characteristics such as low toxicity, low boiling point, and good fluidity.

[0003] Tetrahydrofuran is widely used as a solvent for surface coatings, anticorrosive coatings, printing inks, tapes, and film coatings, and is also used as a reaction solvent. When used for electroplating aluminum liquid, the thickness of the aluminum layer can be arbitrarily controlled and the surface is bright. Tetrahydrofuran itself can be polycondensed (by cationic initiation ring-opening and then polymerization) into polytetramethylene ether glycol (PTMEG), also known as tetrahydrofuran homopolyether. PTMEG and toluene diisocyanate (TDI) are used to make special rubbers with good wear resistance, oil resistance, low-temperature performance, and high strength; and with dimethyl terephthalate and 1,4-butanediol to make block polyether polyester elastic Chemicalbook materials. PTMEG with a relative molecular mass of 2000 and 4,4'-methylenebis(phenyl isocyanate) (MDI) are used as raw materials for polyurethane elastic fibers (spandex, i.e., SPANDEX fibers), special rubbers, and some special-purpose coatings. In terms of organic synthesis, it is used in the production of tetrahydrothiophene, 1,4-dichloroethane, 2,3-dichlorotetrahydrofuran, valerolactone, butyrolactone, and pyrrolidone, etc. In the pharmaceutical industry, tetrahydrofuran is used in the synthesis of carbetapentane, rifamycin, progesterone, and some hormone drugs. Tetrahydrofuran is treated with hydrogen sulfide to produce tetrahydrothiophen, which can be used as an odorant (recognition additive) in fuel gas. Tetrahydrofuran can also be used as a surface treatment agent for synthetic leather.

[0004] In the process of preparing tetrahydrofuran by catalytic dehydration cyclization of 1,4-butanediol (BDO), the tetrahydrofuran produced by the reaction needs to be dehydrated to obtain an anhydrous product. Currently, the more commonly used dehydration process is the two-tower variable-pressure rectification process. In the tetrahydrofuran dehydration process, since the product at the top of the pressurized tower carries a large amount of water and needs to be returned to the atmospheric tower for repeated distillation, the working load of the two towers is increased, and the operating energy consumption of the entire system is improved. In order to reduce the quantity of materials for repeated distillation and lower the energy consumption, finding a method for dehydrating the product has become a common topic in the industry. Summary of the Invention

[0005] The purpose of the present invention is to provide a method and device for refining tetrahydrofuran, a by-product of 1,4-butanediol dehydrogenation, by coupling a tower and a membrane.

[0006] For the above purposes, the present invention adopts the following technical solutions:

[0007] An apparatus for refining tetrahydrofuran, a by-product of 1,4-butanediol dehydrogenation, by coupling a tower and a membrane, comprising a membrane-coupled tower, a membrane module, a post-membrane tower, and a tetrahydrofuran tower connected in sequence. The material from the tetrahydrofuran raw material storage tank enters the middle of the membrane-coupled tower after being preheated by a preheater. The top of the membrane-coupled tower is divided into two pipelines. One pipeline is connected to the membrane module, and the other pipeline is connected to the shell side of the second reboiler. The outlet of the shell side of the second reboiler is connected to the upper part of the membrane-coupled tower. The upstream side of the membrane of the membrane module is connected to the middle of the post-membrane tower. The light components at the top of the post-membrane tower enter the next-stage methanol distillation tower for distillation. The side line is connected to the reflux of the tetrahydrofuran back to the membrane-coupled tower. The bottom of the tower is connected to the middle of the tetrahydrofuran tower. The bottom of the post-membrane tower is also connected to the tube side of the second reboiler. The target product with a water content ≤ 0.02% and tetrahydrofuran ≥ 99.9% is obtained at the top of the tetrahydrofuran tower.

[0008] Further, reboilers are connected to the bottoms of the membrane-coupled tower, the post-membrane tower, the tetrahydrofuran tower, and the methanol distillation tower.

[0009] Further, the membrane module includes multiple-stage reaction membranes and a supplementary heater. Each stage of reaction membrane and the supplementary heater are arranged alternately. The upstream side of each stage of reaction membrane is connected to the inlet of the supplementary heater. The outlet of the supplementary heater is connected to the inlet of the next-stage reaction membrane until the upstream side of the last-stage reaction membrane obtains the finished gas phase. The downstream side of each stage of reaction membrane is connected to a permeate condenser, and a vacuum unit is connected to the permeate condenser. A superheater is provided on the inlet pipe of the first-stage reaction membrane.

[0010] Further, the pipeline at the top of the post-membrane tower is connected to the middle of the methanol distillation tower through a condenser. The mixed distillate of tetrahydrofuran and water is obtained after condensation at the top. The bottom of the tower is a mixture of water and methanol.

[0011] The present invention also claims a method for refining tetrahydrofuran, a by-product of 1,4-butanediol dehydrogenation, by coupling a tower and a membrane using the above apparatus, comprising the following steps:

[0012] (1) The tetrahydrofuran raw material and the discharge from the bottom of the membrane-coupled tower are preheated and then sent to the middle of the tower for continuous pressurized distillation operation in the membrane-coupled tower. The light components are enriched towards the top of the tower under the action of heat sources, and the azeotrope of tetrahydrofuran and water is taken out at the top. Part of the gas phase at the top is sent to the membrane reaction module to further remove the water in the azeotropic composition, and part is sent to the heating reboiler of the post-membrane tower, where it is condensed by itself and then pumped back to the top of the membrane-coupled tower for reflux.

[0013] (2) The overhead gas phase from the membrane-coupled tower enters the membrane module. The temperature of each stage of the reaction membrane in the membrane module increases successively. The water and a small amount of solvent in the overhead gas phase permeate from the upstream side of the membrane to the downstream side of the membrane through the membrane module. The finished product with a water content ≤ 1% is obtained on the upstream side of the last-stage reaction membrane, and the finished product vapor is sent to the post-membrane tower. On the downstream side of each stage of the reaction membrane, a vapor partial pressure difference of components on both sides of the membrane is formed by connecting a vacuum unit. The permeate vapor enters the condenser under the suction of the vacuum unit. After the condensed permeate is discharged by the permeate pump, it is pumped to the feed buffer tank of the membrane-coupled tower;

[0014] (3) The gas-phase material dehydrated by the membrane module is sent to the post-membrane tower for pressurized continuous operation. The methanol light components are taken out from the top of the tower and enter the next-stage distillation tower for distillation, and a part of the tetrahydrofuran with a high water content is taken out from the side line and returned to the membrane-coupled tower for reflux. The bottom material of the tower enters the middle part of the tetrahydrofuran tower, and the bottom material of the tower contains no water and no components lighter than tetrahydrofuran;

[0015] (4) After the bottom material of the post-membrane tower enters the middle part of the tetrahydrofuran tower, vacuum continuous distillation is carried out. The qualified tetrahydrofuran product is distilled out from the top of the tower, with a water content ≤ 0.02% and THF ≥ 99.9%; the bottom is the crude butanol product.

[0016] Further, the methanol light components discharged from the top of the post-membrane tower are sent to the middle part of the methanol distillation tower. The extraction water is fed from the middle and upper part of the tower for atmospheric continuous operation. The top temperature of the methanol distillation tower is 64 °C, the bottom temperature is 100 °C, and the pressure inside the tower is 0.1 MPa; the light components are enriched towards the top of the tower under the action of heat source through the trays, and tetrahydrofuran and water are taken out from the top of the tower and sent to the feed mother liquor tank of Party A; the water and methanol mixture at the bottom of the tower is pumped to the storage tank.

[0017] Preferably, the top temperature of the membrane-coupled tower is 132 °C, the bottom temperature is 153 °C, and the pressure inside the tower is 0.4 MPa.

[0018] Preferably, the temperature of the first-stage reaction membrane of the membrane module is 132, the reaction pressure is 0.2 MPa, the temperature of the last-stage reaction membrane is 140 °C, and the reaction pressure is 0.35 MPa.

[0019] Preferably, the top temperature of the post-membrane tower is 85 °C, the bottom temperature is 117 °C, and the pressure inside the tower is 0.2 MPa; the top temperature of the tetrahydrofuran tower is 55 °C, the bottom is 107 °C, and the inside of the tetrahydrofuran tower is in a negative pressure state.

[0020] Further, the composition of the tetrahydrofuran raw material is recorded by weight percentage: water 27%, THF 43%, n-butanol 21%, methanol 1%, n-propanol 0.37%, butanone 0.73%, 2-methyltetrahydrofuran 0.1%, 3-methyltetrahydrofuran 0.1%, and the balance is high-boiling impurities.

[0021] Furthermore, the requirements for the feed liquid entering the membrane module are as follows: the water content in the tetrahydrofuran distillate is about 20 wt.%, the pH value ranges from 6.5 to 8.5, the conductivity < 5 μS / cm, the chloride ion content ≤ 20 ppm, without pigments, salts, sugars, solid particles, colloids, acidic, alkaline components or other substances that may contaminate the equipment and membrane materials. After evaporation, there is no residue and no color change, and the various indicators of the raw material should be maintained normal and stable for a long time.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] The method provided by the present invention can effectively remove the moisture in the by-product tetrahydrofuran of 1,4-butanediol dehydrogenation, achieve the purpose of purifying tetrahydrofuran, obtain a product with a water content ≤ 0.02% and THF ≥ 99.9%, and the recovery rate of tetrahydrofuran reaches more than 98%.

[0024] The present invention adopts the mode of membrane column coupling in the process, introducing the membrane dehydration technology. Compared with the traditional pressure swing distillation process, the circulation volume of the tetrahydrofuran and water azeotropic system is reduced by 60%, effectively reducing the energy consumed by the circulation loss; at the same time, this process adopts the heat coupling technology, and the heat sources of the latter two towers are both provided by the gas phase at the top of the first tower, reducing the steam energy consumption for heating the tower kettle and the cooling water energy consumption for condensing the gas phase; the comprehensive energy consumption is reduced by 43%. The present invention further separates and purifies the methanol-tetrahydrofuran-water azeotropic system generated by the distillation at the top of the membrane through extractive distillation, collects the tetrahydrofuran therein, improves the recovery rate of tetrahydrofuran, solves the problem of separating and purifying the by-product tetrahydrofuran of 1,4-butanediol dehydrogenation in the whole process, reduces the waste liquid discharge, and improves the resource utilization rate. This process is controlled by DCS, with a high degree of automation, many safety interlock controls, stable control and high safety. Brief Description of the Drawings

[0025] Figure 1 is the process flow diagram of Example 1;

[0026] Figure 2 is the process flow diagram of the methanol distillation column;

[0027] Figure 3 is the structural schematic diagram of the membrane module.

[0028] Among them, the membrane coupling tower T101, the membrane module V1, the post-membrane tower T102, the tetrahydrofuran tower T103, the methanol distillation tower T104, the preheater E1, the second reboiler E2, the reaction membrane V101, the make-up heater V102, the permeate condenser E3, the superheater E4, and the vacuum unit VP1. Detailed Embodiments

[0029] Example 1

[0030] An apparatus for refining tetrahydrofuran, a by-product of 1,4-butanediol dehydrogenation, by coupling a tower and a membrane has a structure as follows Figures 1 - 3 shown, which includes a membrane-coupled tower T101, a membrane module V1, a post-membrane tower T102, and a tetrahydrofuran tower T103 connected in sequence. The material from the tetrahydrofuran raw material storage tank enters the middle of the membrane-coupled tower T101 after being preheated by a preheater E1. The top of the membrane-coupled tower T101 is divided into two pipelines. One pipeline is connected to the membrane module V1, and the other pipeline is connected to the shell side of a second reboiler E2. The outlet of the shell side of the second reboiler E2 is connected to the upper part of the membrane-coupled tower T101; the upstream side of the membrane of the membrane module V1 is connected to the middle of the post-membrane tower T102. The light components at the top of the post-membrane tower T102 enter the next-stage methanol distillation tower T104 for distillation. The side line is connected to the tetrahydrofuran to return to the membrane-coupled tower for reflux, and the bottom of the tower is connected to the middle of the tetrahydrofuran tower T103. The bottom of the post-membrane tower T102 is also connected to the tube side of the second reboiler E2; the target product with a water content ≤ 0.02% and THF ≥ 99.9% is obtained at the top of the tetrahydrofuran tower T103.

[0031] Among them, reboilers are connected to the bottoms of the membrane-coupled tower T101, the post-membrane tower T102, the tetrahydrofuran tower T103, and the methanol distillation tower T104.

[0032] Among them, the structure of the membrane module V1 is as follows Figure 3 shown, which includes multiple-stage reaction membranes V101 and a heater V102. Each stage of reaction membrane V101 and heater V102 are arranged alternately. The upstream side of each stage of reaction membrane V101 is connected to the inlet of the heater V102. The outlet of the heater V102 is connected to the inlet of the next-stage reaction membrane V101 until the upstream side of the last-stage reaction membrane V101 obtains the finished gas phase; the downstream side of each stage of reaction membrane V101 is connected to a permeate condenser E3, and a vacuum unit VP1 is connected to the permeate condenser E3; a superheater E4 is provided on the inlet pipe of the first-stage reaction membrane.

[0033] The pipeline at the top of the post-membrane tower T102 is connected to the middle of the methanol distillation tower T104 through a condenser. The mixed distillate of tetrahydrofuran and water is obtained after condensation at the top of the tower, and the bottom of the tower is a mixture of water and methanol.

[0034] Example 2

[0035] Feeding conditions of tetrahydrofuran raw material: water 27%, tetrahydrofuran 43%, n-butanol 21%, methanol 1%, n-propanol 0.37%, methyl ethyl ketone 0.73%, 2-methyltetrahydrofuran 0.1%, 3-methyltetrahydrofuran 0.1%, and the balance is high-boiling impurities.

[0036] A method for refining tetrahydrofuran, a by-product of 1,4-butanediol dehydrogenation, by coupling a tower and a membrane using the apparatus provided in Example 1 includes the following steps:

[0037] (1) The raw material of tetrahydrofuran is preheated with the bottom discharge of the membrane-coupled tower T101 and then fed into the middle of the tower. The membrane-coupled tower T101 operates under pressurized continuous distillation. The top temperature of the tower is 132 °C, the bottom temperature is 153 °C, and the pressure inside the tower is 0.4 MPa. The light components pass through the trays under the action of heat source and concentrate towards the top of the tower. An azeotrope of tetrahydrofuran and water is taken out at the top of the tower. Part of the top gas phase is sent to the membrane reaction module to further remove the water in the azeotropic composition. Part of it is sent to the reboiler of the post-membrane tower T102, condensed by itself, and then pumped back to the top reflux of the membrane-coupled tower.

[0038] (2) The top gas phase from the membrane-coupled tower T101 enters the membrane module V1. The temperature of each stage of the reaction membrane in the membrane module increases in turn. The temperature of the first-stage reaction membrane V101 is 132, the reaction pressure is 0.2 MPa, the temperature of the last-stage reaction membrane V101 is 140 °C, and the reaction pressure is 0.35 MPa. The water and a small amount of solvent in the top gas phase permeate from the upstream side of the membrane to the downstream side of the membrane through the membrane module. A finished product steam with a water content ≤ 1% is obtained on the upstream side of the last-stage reaction membrane V101. The content of THF in the finished product steam is 67.8%. The finished product steam is sent to the post-membrane tower T102. The downstream side of each stage of the reaction membrane V101 is connected to a vacuum unit to form a vapor partial pressure difference between the upstream and downstream sides of the membrane. The permeate steam enters the permeate condenser E3 under the suction of the vacuum unit VP1. After the condensed permeate is discharged by the permeate pump, it is pumped to the feed buffer tank of the membrane-coupled tower T101.

[0039] (3) The gas-phase material dehydrated by the membrane module is sent to the post-membrane tower T102 for pressurized continuous operation. The top temperature of the tower is 85 °C, the bottom temperature is 117 °C, and the pressure inside the tower is 0.2 MPa. The methanol light components are taken out from the top of the tower and enter the next-stage methanol distillation tower T104 for distillation, and part of the tetrahydrofuran with a high water content is taken out from the side line and returned to the membrane-coupled tower for reflux. The bottom material of the tower enters the middle of the tetrahydrofuran tower T103. The bottom material of the tower contains no water and no components with a boiling point lower than that of tetrahydrofuran. The water content in the bottom material is ≤ 0.01%.

[0040] (4) After the bottom material of the post-membrane tower T102 enters the middle of the tetrahydrofuran tower T103, vacuum continuous distillation is carried out. The top temperature of the tetrahydrofuran tower T103 is 55 °C, and the bottom is 107 °C. The tetrahydrofuran tower T103 is in a negative pressure state. A qualified tetrahydrofuran product is distilled out from the top of the tower, with a water content ≤ 0.02% and THF ≥ 99.9%. The recovery rate of the tetrahydrofuran product reaches 98%; the bottom is the crude butanol product.

[0041] (1) Since the methanol light components discharged from the top of the post-membrane tower T102 contain a certain amount of tetrahydrofuran, it is a mixed liquid of methanol and tetrahydrofuran. This mixed liquid can be sent to the middle part of another methanol distillation tower T104. The extraction water is fed from the middle and upper part of the tower, and it is continuously operated at atmospheric pressure. The top temperature of the methanol distillation tower T104 is 64 °C, the bottom temperature is 100 °C, and the pressure inside the tower is 0.1 MPa. Under the action of the heat source, the light components pass through the trays and are enriched towards the top of the tower. Tetrahydrofuran and water are withdrawn from the top of the tower and sent to the feed mother liquor tank of Party A. The water and methanol mixture at the bottom of the tower is pumped to the temporary storage tank. The methanol light components can also be temporarily stored in the storage tank. After the distillation operation of the gas-phase material after the membrane component dehydration in the post-membrane tower T102 is stopped, the material in the post-membrane tower T102 is emptied, and the post-membrane tower T102 is used as the distillation tower for methanol light components, and its process parameters are the same as those of the methanol distillation tower T104.

[0042] Among them, the requirements for the feed liquid entering the membrane component are as follows: the water content in the tetrahydrofuran distillate is about 20 wt.%, the pH value ranges from 6.5 to 8.5, the conductivity < 5 μS / cm, the chloride ion content ≤ 20 ppm, it does not contain pigments, salts, sugars, solid particles, colloids, acidic, basic components or other substances that may contaminate the equipment and membrane materials. After evaporation, there is no residue and no color change, and the various indicators of the raw material should be kept normal and stable for a long time.

Claims

1. An apparatus for refining tetrahydrofuran, a by-product of 1,4-butanediol dehydrogenation, by coupling a tower and a membrane, characterized in that, It includes a membrane-coupled tower, a membrane module, a post-membrane tower, and a tetrahydrofuran tower connected in sequence. The material from the tetrahydrofuran raw material storage tank is preheated by a preheater and then enters the middle of the membrane-coupled tower. The top of the membrane-coupled tower is divided into two pipelines. One pipeline is connected to the membrane module, and the other pipeline is connected to the shell side of the second reboiler. The outlet of the shell side of the second reboiler is connected to the upper part of the membrane-coupled tower; the upstream side of the membrane of the membrane module is connected to the middle of the post-membrane tower. The light components at the top of the post-membrane tower enter the next-stage methanol distillation column for distillation. The side line is connected to the reflux of the tetrahydrofuran back to the membrane-coupled tower, and the bottom of the tower is connected to the middle of the tetrahydrofuran tower. The bottom of the post-membrane tower is also connected to the tube side of the second reboiler; the target product with a water content ≤ 0.02% and tetrahydrofuran ≥ 99.9% is obtained at the top of the tetrahydrofuran tower; the membrane module includes multiple-stage reaction membranes and a supplementary heater. Each stage of the reaction membrane and the supplementary heater are arranged alternately. The upstream side of each stage of the reaction membrane is connected to the inlet of the supplementary heater, and the outlet of the supplementary heater is connected to the inlet of the next-stage reaction membrane until the upstream side of the last-stage reaction membrane obtains the finished gas phase; the downstream side of each stage of the reaction membrane is connected to a permeate condenser, and a vacuum unit is connected to the permeate condenser; a superheater is provided on the inlet pipe of the first-stage reaction membrane.

2. The device according to claim 1, characterized in that, Reboilers are connected to the bottoms of the membrane-coupled tower, the post-membrane tower, the tetrahydrofuran tower, and the methanol distillation column.

3. The device according to claim 1 or 2, characterized in that, The pipeline at the top of the post-membrane tower is connected to the middle of the methanol distillation column through a condenser. A mixed distillate of tetrahydrofuran and water is obtained after condensation at the top, and the bottom of the tower is a mixture of water and methanol.

4. A method for purifying tetrahydrofuran, a byproduct of 1,4-butanediol dehydrogenation, by coupling a tower and a membrane using the device according to any one of claims 1-3, characterized in that, It includes the following steps: The tetrahydrofuran raw material and the discharged material from the bottom of the membrane-coupled tower are preheated and then sent to the middle of the tower for continuous pressurized distillation operation of the membrane-coupled tower; the light components are enriched towards the top of the tower through the trays under the action of heat source. An azeotrope of tetrahydrofuran and water is taken out at the top. Part of the gas phase at the top is sent to the membrane reaction module to further remove the water in the azeotropic composition, and part is sent to the reboiler of the post-membrane tower and then condensed by itself, and then pumped back to the top of the membrane-coupled tower for reflux. The gas phase at the top from the membrane-coupled tower enters the membrane module. The temperatures of the reaction membranes at all levels in the membrane module increase sequentially. The water and a small amount of solvent in the gas phase at the top permeate from the upstream side of the membrane to the downstream side of the membrane through the membrane module. The finished product with a water content ≤ 1% is obtained on the upstream side of the last-stage reaction membrane. The finished product steam is sent to the post-membrane tower. The downstream side of each stage of the reaction membrane forms a steam partial pressure difference between the two sides of the membrane by connecting a vacuum unit. The permeate steam enters the condenser under the suction of the vacuum unit. After the condensed permeate is discharged by the permeate pump, it is pumped to the feed buffer tank of the membrane-coupled tower. The gas-phase material dehydrated by the membrane module is sent to the post-membrane tower for continuous pressurized operation. The methanol light components are taken out from the top and enter the next-stage methanol distillation column for distillation, and a part of the tetrahydrofuran with a high water content is taken out from the side line and refluxed to the membrane-coupled tower. The bottom material of the tower enters the middle of the tetrahydrofuran tower, and the bottom material of the tower does not contain water or components lighter than tetrahydrofuran. After the bottom material of the post-membrane tower enters the middle of the tetrahydrofuran tower, it is subjected to continuous vacuum distillation. The qualified tetrahydrofuran product is distilled at the top, with a water content ≤ 0.02% and tetrahydrofuran ≥ 99.9%; the bottom of the tower is the crude butanol product.

5. The method according to claim 4, wherein The methanol light components discharged from the top of the post-membrane tower are sent to the middle of the methanol rectification tower. The extraction water is fed from the upper middle part of the tower. It operates continuously at atmospheric pressure. The top temperature of the methanol rectification tower is 64 °C, the bottom temperature is 100 °C, and the pressure inside the tower is 0.1 MPa; under the action of the heat source, the light components pass through the trays and are enriched towards the top of the tower. Tetrahydrofuran and water are withdrawn from the top and sent to the feed mother liquor tank of Party A; the water and methanol mixture at the bottom of the tower is pumped to the temporary storage tank.

6. The method according to claim 5, wherein The top temperature of the membrane-coupled tower is 132 °C, the bottom temperature is 153 °C, and the pressure inside the tower is 0.4 MPa.

7. The method according to claim 5, characterized in that, The temperature of the first-stage reaction membrane of the membrane module is 132, the reaction pressure is 0.2 MPa, the temperature of the last-stage reaction membrane is 140 °C, and the reaction pressure is 0.35 MPa.

8. The method according to claim 5, characterized in that The top temperature of the post-membrane tower is 85 °C, the bottom temperature is 117 °C, and the pressure inside the tower is 0.2 MPa; the top temperature of the tetrahydrofuran tower is 55 °C, the bottom is 107 °C, and the inside of the tetrahydrofuran tower is in a negative pressure state.

9. The method according to any one of claims 4-8, characterized in that, The composition of the tetrahydrofuran raw material is recorded by weight percentage: water 27%, tetrahydrofuran 43%, n-butanol 21%, methanol 1%, n-propanol 0.37%, methyl ethyl ketone 0.73%, 2-methyltetrahydrofuran 0.1%, 3-methyltetrahydrofuran 0.1%, and the balance is high-boiling impurities.

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