Separation and purification method of tetrahydrofuran-water-ethanol-n-butanol mixed solution

Abstract

The invention discloses a separation and purification method of a tetrahydrofuran-water-ethanol-n-butanol mixed solution, and relates to the technical field of chemical separation. The method comprises the following steps: introducing a mixed solution into a high-pressure rectifying tower, and separating to obtain a tetrahydrofuran-n-butyl alcohol mixed solution and a tetrahydrofuran-water-ethanol mixed solution; introducing the tetrahydrofuran-n-butyl alcohol mixed solution into a normal-pressure rectifying tower to obtain a high-purity tetrahydrofuran product and an n-butyl alcohol solution; introducing the tetrahydrofuran-water-ethanol mixed solution into a normal-pressure rectifying tower, introducing water, and separating to obtain wastewater and a tetrahydrofuran-water-ethanol mixed solution with relatively high water content; and introducing the high-pressure rectifying tower into a liquid-liquid separator, refluxing the separated water phase to the normal-pressure rectifying tower, and refluxing the oil phase to the high-pressure rectifying tower. The method is simple in process and low in energy consumption, the recovery rate of tetrahydrofuran can reach 99.8% or above, the product purity reaches 99.95%, and the method is suitable for industrial production.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical separation, and particularly relates to a method for separating and purifying a mixed solution of tetrahydrofuran - water - ethanol - n - butanol, which is especially suitable for the separation and purification of a multi - component azeotropic system. Background Art

[0002] Tetrahydrofuran (THF), ethanol, water, and n - butanol are important chemical raw materials, which are widely used in industries such as medicine, chemical engineering, pesticides, and dyes. Tetrahydrofuran is a medium - polarity aprotic solvent, which is often used as a solvent, reaction medium, and starting material in chemical reactions. Ethanol is not only an important industrial solvent but also used in the production of chemicals such as acetaldehyde and ether, and is also widely used in the food, beverage, and medical fields. n - Butanol is mainly used in the production of plasticizers, paint additives, and pharmaceuticals, etc.

[0003] In actual chemical production, a mixed solution of tetrahydrofuran, ethanol, water, and n - butanol often forms during the production process of tetrahydrofuran. Since these components are prone to form azeotropes, traditional single distillation or azeotropic distillation methods are difficult to effectively separate, resulting in low recovery rate and purity of tetrahydrofuran. Therefore, developing an efficient and energy - saving separation and purification method has important industrial application value. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for separating and purifying a mixed solution of tetrahydrofuran - water - ethanol - n - butanol. Through the synergistic effect of variable - pressure distillation and a liquid - liquid separator, the efficient separation and purification of tetrahydrofuran are realized, and at the same time, the recovery rate and product purity of tetrahydrofuran are improved.

[0005] To achieve the above - mentioned purpose, the present invention adopts the following technical solutions:

[0006] A method for separating and purifying a mixed solution of tetrahydrofuran - water - ethanol - n - butanol, comprising the following steps:

[0007] Step 1: Feed the mixed solution of tetrahydrofuran - water - ethanol - n - butanol into a high - pressure distillation column, and separate the bottom product and the top product in the high - pressure distillation column. The bottom product is a mixed solution of tetrahydrofuran - n - butanol, and the top product is a mixed solution of tetrahydrofuran - water - ethanol;

[0008] Step 2: Feed the mixed solution of tetrahydrofuran - n - butanol obtained in Step 1 into an atmospheric distillation column 1, and separate the top product and the bottom product in the atmospheric distillation column 1. The top product is a high - purity tetrahydrofuran product, and the bottom product is an n - butanol solution;

[0009] Step 3: Feed the tetrahydrofuran-water-ethanol mixed solution obtained in Step 1 into the atmospheric distillation column 2, and at the same time feed water into the atmospheric distillation column 2. Separate the overhead product and the bottom product in the atmospheric distillation column 2. The bottom product is the wastewater containing tetrahydrofuran and ethanol, and the overhead product is the tetrahydrofuran-water-ethanol mixed solution with a high water content.

[0010] Step 4: Feed the tetrahydrofuran-water-ethanol mixed solution obtained in Step 3 into a liquid-liquid separator to separate the aqueous phase and the oil phase. The oil phase is refluxed to the high-pressure distillation column.

[0011] Step 6: Send the wastewater obtained in Step 3 for wastewater treatment.

[0012] Step 9: Reflux the aqueous phase separated in Step 4 to the atmospheric distillation column 2.

[0013] Furthermore, the mass fractions of the components in the tetrahydrofuran-water-ethanol-n-butanol mixed solution are as follows:

[0014] Tetrahydrofuran: 98.1 - 99.0%,

[0015] Ethanol: 0.03 - 0.05%,

[0016] Water: 0.3 - 0.5%,

[0017] n-Butanol: 0.95 - 1.15%.

[0018] Furthermore, the operating conditions of the high-pressure distillation column are as follows:

[0019] Operating pressure: 5 - 8 bar,

[0020] Overhead temperature: 108.1 - 108.3 °C,

[0021] Bottom temperature: 116.1 - 116.7 °C.

[0022] Furthermore, the operating conditions of the atmospheric distillation column 1 are as follows:

[0023] Overhead temperature: 65.7 - 65.8 °C,

[0024] Bottom temperature: 113.7 - 115.2 °C.

[0025] Furthermore, the mass fractions of the components in the overhead product of the atmospheric distillation column 1 are as follows:

[0026] Tetrahydrofuran: 99.95%,

[0027] Ethanol: <0.005%,

[0028] Water: <0.006%,

[0029] n-Butanol: the remaining part.

[0030] Further, the operating conditions of the atmospheric distillation column 2 are as follows:

[0031] Temperature at the top of the column: 63.0 - 63.3 °C,

[0032] Temperature at the bottom of the column: 78.0 - 80.0 °C.

[0033] Further, the mass ratio of the mixed solution feed to the water feed in the atmospheric distillation column 2 is 3.0 - 4.0:1.

[0034] Further, the mass fraction of tetrahydrofuran in the bottom product of the atmospheric distillation column 2 is less than 98.0%.

[0035] Further, the operating conditions of the liquid-liquid separator are as follows:

[0036] The aqueous phase is refluxed to the atmospheric distillation column 2,

[0037] The oil phase is refluxed to the high-pressure distillation column.

[0038] Further, the recovery rate of the tetrahydrofuran product can reach over 99.8%, and the purity of the tetrahydrofuran product reaches 99.95%.

[0039] Further, the total height of the packing in the high-pressure distillation column is 16000 mm, divided into four sections, with the heights of each section being 3200 mm, 3200 mm, 4800 mm, and 4800 mm respectively.

[0040] Further, the total height of the packing in the atmospheric distillation column 1 is 8000 mm, divided into two sections, with the heights of each section being 4000 mm and 4000 mm respectively.

[0041] Further, the total height of the packing in the atmospheric distillation column 2 is 8000 mm, divided into three sections, with the heights of each section being 1200 mm, 800 mm, and 1200 mm respectively.

[0042] Further, part of the top product of the high-pressure distillation column is refluxed and part is withdrawn. The withdrawal flow rate is 25.0 kg / h, with a mass fraction of 91.90% tetrahydrofuran, 0.37% ethanol, and 7.73% water.

[0043] Further, part of the top product of the atmospheric distillation column 1 is refluxed and part is withdrawn. The withdrawal flow rate is 295.20 kg / h, with a mass fraction of 99.995% tetrahydrofuran and 0.005% ethanol.

[0044] The advantages and effects of the present invention are as follows: By combining traditional pressure-swing distillation and liquid-liquid separation, and adding water to the vacuum distillation column, not only the separation of ethanol is achieved, but also the components at the top of the column meet the conditions for liquid-liquid separation. The liquid-liquid separator is used to separate water and tetrahydrofuran, simplifying the process and reducing the energy consumption required for separation. While meeting the requirement that the mass fraction of the tetrahydrofuran product reaches 99.95%, the recovery rate of tetrahydrofuran can be over 99.8%. Description of the Drawings

[0045] Figure 1 It is a flow chart of the method for separating and purifying a tetrahydrofuran-water-ethanol-n-butanol mixed solution of the present invention.

[0046] Description of the Reference Numerals

[0047] ① High-pressure distillation column

[0048] ② Atmospheric distillation column 1

[0049] ③ Atmospheric distillation column 2

[0050] ④ Liquid-liquid separator

[0051] 1 Feed

[0052] 2 Tetrahydrofuran-n-butanol mixed solution at the bottom of the high-pressure distillation column

[0053] 3 Tetrahydrofuran-water-ethanol mixed solution at the top of the high-pressure distillation column

[0054] 4 Waste water at the bottom of the atmospheric distillation column 2

[0055] 5 Tetrahydrofuran-water-ethanol mixed solution with a high water content at the top of the atmospheric distillation column 2

[0056] 6 Aqueous phase product of the liquid-liquid separator

[0057] 7 Oil phase product of the liquid-liquid separator

[0058] 8 Water feed to the atmospheric distillation column 2

[0059] 9 n-Butanol solution at the bottom of the atmospheric distillation column 1

[0060] 10 High-purity tetrahydrofuran product at the top of the atmospheric distillation column 1 Detailed Embodiments

[0061] The distillation column in this embodiment not only includes the column body, but may also include related pumps, pipelines, valves, control systems and other related supporting equipment and instrument systems configured for the distillation column body to achieve distillation.

[0062] In this embodiment, the transportation of each material can be controlled for flow rate by pipelines, pumps, valves, and control systems, and the temperature of the material can be adjusted by various equipment such as heaters and heat exchangers.

[0063] The phase separation tank in this embodiment is not limited to a strict tank body, but can also be various equipment for phase separation such as a phase separation tower and a phase separation tank. It can also include related pumps, pipelines, inventions, control systems and other related supporting equipment and instrument systems configured for the phase separation tank to achieve phase separation.

[0064] The present invention will be described in detail below in conjunction with embodiments and the accompanying drawings, but the protection scope of the present invention is not limited to the following embodiments. Unless otherwise specified, the contents in the embodiments are all weight percentage contents.

[0065] Embodiment 1

[0066] Using a mixed solution of tetrahydrofuran, ethanol, water and n-butanol as raw materials, the composition of the mixed solution to be separated is: 98.5% by mass of tetrahydrofuran, 0.03% of ethanol, 0.5% of water, and 0.97% of n-butanol.

[0067] The operating parameters of the high-pressure rectification tower are: the operating pressure is 0.4 MPa, the total height of the packing is 16000 mm, the packing is divided into four sections, the heights of each section are 3200 mm, 3200 mm, 4800 mm, and 4800 mm respectively, the top temperature of the tower is 108.12 °C, and the bottom temperature of the tower is 116.15 °C; the raw material feed inlet is the starting position of the third section of the packing, the flow rate is 300 kg / h, the oil-phase product inlet of the liquid-liquid separator is the starting position of the second section of the packing, the flow rate is 23.24 kg / h, and the mass fraction is 98.07% of tetrahydrofuran, 0.075% of ethanol, and 1.86% of water.

[0068] Part of the bottom product of the high-pressure rectification tower is refluxed and part is withdrawn. The withdrawal flow rate is 298.24 kg / h, and the mass fraction is 99.02% of tetrahydrofuran, 0.0049% of ethanol, and 0.976% of n-butanol. The withdrawn product is fed into the atmospheric rectification tower 1; part of the top product of the tower is refluxed and part is withdrawn. The withdrawal flow rate is 25.0 kg / h, and the mass fraction is 91.90% of tetrahydrofuran, 0.37% of ethanol, and 7.73% of water. The withdrawn product is fed into the atmospheric rectification tower 2.

[0069] The operating parameters of the atmospheric rectification tower 1 are: the operating pressure is 0.101 MPa, the total height of the packing is 8000 mm, the packing is divided into two sections, the heights of each section are 4000 mm and 4000 mm respectively, and the bottom product of the high-pressure rectification tower enters the atmospheric rectification tower 1 from the bottom; the top temperature of the tower is 65.87 °C, and the bottom temperature of the tower is 113.73 °C.

[0070] For the bottom product of atmospheric distillation column 1, part of it is refluxed and part is withdrawn. The withdrawal flow rate is 3.04 kg / h, with a mass fraction of 4.41% tetrahydrofuran and 95.59% n-butanol. For the top product of the column, part of it is refluxed and part is withdrawn. The withdrawal flow rate is 295.20 kg / h, with a mass fraction of 99.995% tetrahydrofuran and 0.005% ethanol. The recovery rate of tetrahydrofuran is 99.89%.

[0071] The operating parameters of atmospheric distillation column 2 are as follows: the operating pressure is 0.101 MPa, the total height of the packing is 8000 mm, and the packing is divided into three sections with heights of 1200 mm, 800 mm, and 1200 mm respectively. The inlet of the top product of the high-pressure distillation column is at the starting position of the third section of the packing, with a flow rate of 25.0 kg / h. The inlets of water into atmospheric distillation column 2 and the water-phase product of the liquid-liquid separator are at the starting position of the second section of the packing, with flow rates of 8.0 kg / h and 0.76 kg / h respectively. The top temperature is 63.06 °C, and the bottom temperature is 92.55 °C.

[0072] For the bottom product of atmospheric distillation column 2, part of it is refluxed and part is withdrawn. The withdrawal flow rate is 9.76 kg / h, with a mass fraction of 1.85% tetrahydrofuran, 0.77% ethanol, and 97.38% water. For the top product of the column, part of it is refluxed and part is withdrawn. The withdrawal flow rate is 24.0 kg / h, with a mass fraction of 94.98% tetrahydrofuran, 0.07% ethanol, and 4.95% water. The withdrawn product is fed into a liquid-liquid separator.

[0073] The water-phase product and the oil-phase product of the liquid-liquid separator are refluxed to atmospheric distillation column 2 and the high-pressure distillation column respectively.

[0074] Through the synergistic effect of pressure swing distillation and the liquid-liquid separator, the present invention realizes the efficient separation and purification of the tetrahydrofuran-water-ethanol-n-butanol mixed solution. The recovery rate of tetrahydrofuran can reach over 99.8%, and the product purity reaches 99.95%. This method has the advantages of simple process, low energy consumption, and good separation effect, and is suitable for industrial production.

[0075] The embodiments in the present invention are only used to illustrate the present invention and do not constitute a limitation on the scope of the claims. Other substantially equivalent alternatives that can be conceived by those skilled in the art are all within the protection scope of the present invention.

Claims

1. A method for separating and purifying a tetrahydrofuran-water-ethanol-n-butanol mixed solution, characterized in that: The method comprises the following steps: Step 1: passing a tetrahydrofuran-water-ethanol-n-butanol mixed solution into a high-pressure distillation tower, and separating in the high-pressure distillation tower to obtain a bottom product and a top product, wherein the bottom product is a tetrahydrofuran-n-butanol mixed solution, and the top product is a tetrahydrofuran-water-ethanol mixed solution; Step 2: passing the tetrahydrofuran-n-butanol mixed solution obtained in step 1 into an atmospheric distillation tower (1), and separating the top product and the bottom product in the atmospheric distillation tower (1), wherein the top product is a high-purity tetrahydrofuran product, and the bottom product is an n-butanol solution; Step 3: passing the tetrahydrofuran-water-ethanol mixed solution obtained in step 1 into an atmospheric distillation tower (2), and simultaneously passing water into the atmospheric distillation tower (2), and separating in the atmospheric distillation tower (2) to obtain a tower top product and a tower bottom product, wherein the tower bottom product is waste water containing tetrahydrofuran and ethanol, and the tower top product is a tetrahydrofuran-water-ethanol mixed solution having a higher water content; Step 4: passing the tetrahydrofuran-water-ethanol mixed solution obtained in step 3 into a liquid-liquid separator to separate into a water phase and an oil phase, wherein the oil phase is refluxed to a high-pressure distillation tower; Step 5: sending the wastewater obtained in step 3 to wastewater treatment; Step 6: reflux the aqueous phase separated in step 4 to the atmospheric distillation tower (2).

2. The method according to claim 1, characterized in that The mass fraction of each component in the tetrahydrofuran-water-ethanol-n-butanol mixed solution is: Tetrahydrofuran: 98.1-99.0%, Ethanol: 0.03-0.05%, Water: 0.3-0.5%, n-Butanol: 0.95-1.15%.

3. The method according to claim 1, characterized in that: The operating conditions of the high-pressure distillation tower are: Operating pressure: 5-8bar, Tower top temperature: 108.1-108.3℃, Tower bottom temperature: 116.1-116.7℃.

4. The method according to claim 1, characterized in that: The operating conditions of the atmospheric distillation tower (1) are: Tower top temperature: 65.7-65.8℃, Tower bottom temperature: 113.7-115.2℃.

5. The method according to claim 1, characterized in that The mass fraction of each component in the top product of the atmospheric distillation tower (1) is: Tetrahydrofuran: 99.95%, Ethanol: <0.005%, Water: <0.006%, n-Butanol: the remainder.

6. The method according to claim 1, characterized in that The operating conditions of the atmospheric distillation tower (2) are: Tower top temperature: 63.0-63.3℃, Tower bottom temperature: 78.0-80.0℃.

7. The method according to claim 1, characterized in that The mass ratio of the mixed solution feed to the water feed in the atmospheric distillation tower (2) is 3.0-4.0:

1.

8. The method according to claim 1, characterized in that The mass fraction of tetrahydrofuran in the bottom product of the atmospheric distillation tower (2) is less than 98.0%.

9. The method according to claim 1, characterized in that: The operating conditions of the liquid-liquid separator are: the water phase is refluxed to the atmospheric distillation tower (2), and the oil phase is refluxed to the high-pressure distillation tower.

10. The method according to claim 1, characterized in that The recovery rate of the tetrahydrofuran product can reach above 99.8%, and the purity of the tetrahydrofuran product can reach 99.95%.

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