Method for separating tetrahydrofuran from n-heptane-n-hexane-tetrahydrofuran mixed system

Abstract

The invention provides a method for separating tetrahydrofuran from an n-heptane-n-hexane-tetrahydrofuran mixed system, which comprises the following steps: carrying out centrifugal extraction on the n-heptane-n-hexane-tetrahydrofuran mixed system by using water as an extraction agent to obtain a heavy phase discharge material; rectifying the heavy-phase discharged material to obtain a tetrahydrofuran and water azeotrope; the tetrahydrofuran and water azeotrope is subjected to dehydration treatment, and tetrahydrofuran is obtained. According to the method, tetrahydrofuran can be effectively separated from n-heptane-n-hexane-tetrahydrofuran, and the purity of tetrahydrofuran can reach 99.5% or above.

Description

Technical Field

[0001] The present invention belongs to the field of solvent separation and relates to a method for separating tetrahydrofuran from a mixed system of n-heptane - n-hexane - tetrahydrofuran. Background Art

[0002] N-heptane, n-hexane, and tetrahydrofuran are all important organic solvents and are widely used in fields such as organic chemical industry, synthetic pharmaceuticals, and fine chemicals. During the production process, waste liquid composed of these three solvents is often generated. If the solvent separation and reuse of this waste liquid can be achieved, the solvent consumption will be greatly reduced and the cost will be saved. However, due to the azeotropic phenomenon among the solvents in reality, it is very difficult to separate this mixed solvent using ordinary distillation methods.

[0003] Currently, distillation, continuous extraction, and osmotic membrane dehydration technologies are used to efficiently separate and purify the waste liquid, and the waste liquid is converted into usable solvents to the greatest extent. However, this process still has some disadvantages: 1) large water consumption in continuous extraction; 2) low extraction rate of tetrahydrofuran. Summary of the Invention

[0004] In view of the problems existing in the prior art, the present invention provides a method for separating tetrahydrofuran from a mixed system of n-heptane - n-hexane - tetrahydrofuran. The method can effectively separate tetrahydrofuran from n-heptane - n-hexane - tetrahydrofuran, and the purity of tetrahydrofuran can reach more than 99.5%.

[0005] To achieve the above technical effects, the present invention adopts the following technical solutions:

[0006] The present invention provides a method for separating tetrahydrofuran from a mixed system of n-heptane - n-hexane - tetrahydrofuran, and the method includes:

[0007] Centrifugally extracting the mixed system of n-heptane - n-hexane - tetrahydrofuran with water as the extractant to obtain a heavy-phase discharge;

[0008] Distilling the heavy-phase discharge to obtain an azeotrope of tetrahydrofuran and water;

[0009] Performing dehydration treatment on the azeotrope of tetrahydrofuran and water to obtain tetrahydrofuran.

[0010] In the present invention, water is selected as the extractant and combined with centrifugal extraction, which can effectively and selectively separate tetrahydrofuran from the mixed system of n-heptane - n-hexane - tetrahydrofuran. The content of tetrahydrofuran in the light-phase discharge is reduced to <2%, and the content of tetrahydrofuran in the heavy-phase discharge is >12%, with a high extraction rate.

[0011] As a preferred technical solution of the present invention, the rotational speed of the centrifugal extraction is 500 - 1500 rpm, such as 500 rpm, 600 rpm, 700 rpm, 800 rpm, 900 rpm, 1000 rpm, 1100 rpm, 1200 rpm, 1300 rpm, 1400 rpm or 1500 rpm, etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0012] As a preferred technical solution of the present invention, the centrifugal extraction is at least 4 - stage continuous extraction, such as 4 - stage, 5 - stage, 6 - stage, 7 - stage or 8 - stage, etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0013] As a preferred technical solution of the present invention, the flow rate ratio of water to the n - heptane - n - hexane - tetrahydrofuran mixed system is 2.5 - 3.5:1, such as 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1, 3.0:1, 3.1:1, 3.2:1, 3.3:1, 3.4:1 or 3.5:1, etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0014] As a preferred technical solution of the present invention, the light - phase discharge of the centrifugal extraction is n - heptane and / or n - hexane.

[0015] In the present invention, preferably, the light - phase feed flow rate is 660 L / h, the heavy - phase feed flow rate is 1650 - 2310 L / h, and the rotational speed of the centrifugal extraction drum is 1000 r / min, which can ensure the best separation effect, without layering in the discharge of both the light and heavy phases, and good processing efficiency.

[0016] As a preferred technical solution of the present invention, the pre - fraction at 60 - 70°C in the rectification is the tetrahydrofuran - water azeotrope, such as the pre - fraction at 60°C, 61°C, 62°C, 63°C, 64°C, 65°C, 66°C, 67°C, 68°C, 69°C or 70°C, etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0017] As a preferred technical solution of the present invention, the content of tetrahydrofuran in the tetrahydrofuran - water azeotrope is 90 - 99 wt%, such as 90 wt%, 91 wt%, 92 wt%, 93 wt%, 94 wt%, 95 wt%, 96 wt%, 97 wt%, 98 wt% or 99 wt%, etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0018] In the present invention, the conditions of rectification are the conventional conditions in the art for separating the tetrahydrofuran - water azeotrope by rectification, and the specific conditions are not further defined herein.

[0019] As a preferred technical solution of the present invention, the dehydration treatment is membrane dehydration treatment.

[0020] As a preferred technical solution of the present invention, the water content of tetrahydrofuran after the dehydration treatment is less than 0.5 wt%, such as 0.5 wt%, 0.4 wt%, 0.3 wt%, 0.2 wt% or 0.1 wt%, etc., but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0021] In the present invention, the conditions for membrane dehydration are the conventional dehydration conditions for tetrahydrofuran in the art, and specific conditions are not further defined herein.

[0022] As a preferred technical solution of the present invention, the separation of tetrahydrofuran from the n-heptane - n-hexane - tetrahydrofuran mixed system includes:

[0023] Centrifugal extraction is performed on the n-heptane - n-hexane - tetrahydrofuran mixed system with water as the extractant. The centrifugal extraction is at least 4-stage continuous extraction, the rotation speed is 500 - 1500 rpm, and the flow rate ratio of water to the n-heptane - n-hexane - tetrahydrofuran mixed system is 2.5 - 3.5:1 to obtain a heavy-phase discharge;

[0024] Rectification is performed on the heavy-phase discharge to obtain a tetrahydrofuran - water azeotrope. The pre-fraction at 60 - 70 °C in the rectification is the tetrahydrofuran - water azeotrope, and the content of tetrahydrofuran in the tetrahydrofuran - water azeotrope is 90 - 99%;

[0025] The tetrahydrofuran - water azeotrope is subjected to membrane dehydration treatment to obtain tetrahydrofuran, and the water content of tetrahydrofuran after the dehydration treatment is less than 0.5 wt%.

[0026] Compared with the prior art solutions, the present invention has at least the following beneficial effects:

[0027] The present invention provides a method for separating tetrahydrofuran from an n-heptane - n-hexane - tetrahydrofuran mixed system. The method can effectively separate tetrahydrofuran from the n-heptane - n-hexane - tetrahydrofuran, and the purity of tetrahydrofuran can reach more than 99.5%. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a process flow diagram of the method for separating tetrahydrofuran from the n-heptane - n-hexane - tetrahydrofuran mixed system provided by the specific embodiment of the present invention.

[0029] The following further details the present invention. However, the following examples are merely simple examples of the present invention and do not represent or limit the scope of the protection of the present invention. The scope of protection of the present invention is subject to the claims. Detailed Embodiments

[0030] The technical solution of the present invention will be further described below in conjunction with the accompanying drawings and through specific embodiments.

[0031] To better illustrate the present invention and facilitate understanding of its technical solution, typical but non-limiting embodiments of the present invention are as follows:

[0032] Example 1

[0033] This example provides a method for separating tetrahydrofuran from a n-heptane - n-hexane - tetrahydrofuran mixed system. The process is as Figure 1 shown, and the method includes:

[0034] Centrifugal extraction is performed on the n-heptane - n-hexane - tetrahydrofuran mixed system with water as the extractant. The centrifugal extraction is a 5-stage continuous extraction with a rotation speed of 500 rpm. The flow rate of n-heptane - n-hexane - tetrahydrofuran is 660 L / h, and the flow rate of water is 1650 L / h to obtain a heavy-phase discharge;

[0035] Rectification is performed on the heavy-phase discharge to obtain a tetrahydrofuran - water azeotrope. The pre-fraction at 65°C in the rectification is the tetrahydrofuran - water azeotrope, and the content of tetrahydrofuran in the tetrahydrofuran - water azeotrope is 95 wt%, with the balance being water;

[0036] Membrane dehydration treatment is performed on the tetrahydrofuran - water azeotrope to obtain tetrahydrofuran.

[0037] Example 2

[0038] This example provides a method for separating tetrahydrofuran from a n-heptane - n-hexane - tetrahydrofuran mixed system. The method includes:

[0039] Centrifugal extraction is performed on the n-heptane - n-hexane - tetrahydrofuran mixed system with water as the extractant. The centrifugal extraction is a 4-stage continuous extraction with a rotation speed of 1500 rpm. The flow rate of n-heptane - n-hexane - tetrahydrofuran is 660 L / h, and the flow rate of water is 2310 L / h to obtain a heavy-phase discharge;

[0040] Rectification is performed on the heavy-phase discharge to obtain a tetrahydrofuran - water azeotrope. The pre-fraction at 65°C in the rectification is the tetrahydrofuran - water azeotrope, and the content of tetrahydrofuran in the tetrahydrofuran - water azeotrope is 95 wt%, with the balance being water;

[0041] Membrane dehydration treatment is performed on the tetrahydrofuran - water azeotrope to obtain tetrahydrofuran.

[0042] Example 3

[0043] This embodiment provides a method for separating tetrahydrofuran from a n-heptane-n-hexane-tetrahydrofuran mixed system, and the method includes:

[0044] Centrifugally extracting the n-heptane-n-hexane-tetrahydrofuran mixed system with water as the extractant. The centrifugal extraction is a 4-stage continuous extraction, the rotation speed is 1000 rpm, the flow rate of the n-heptane-n-hexane-tetrahydrofuran is 660 L / h, and the flow rate of water is 1980 L / h to obtain a heavy-phase discharge;

[0045] Rectifying the heavy-phase discharge to obtain a tetrahydrofuran-water azeotrope. In the rectification, the fore-fraction at 65 °C is the tetrahydrofuran-water azeotrope, and the content of tetrahydrofuran in the tetrahydrofuran-water azeotrope is 95 wt%, and the balance is water;

[0046] Performing membrane dehydration treatment on the tetrahydrofuran-water azeotrope to obtain tetrahydrofuran.

[0047] Example 4

[0048] In this embodiment, except that the flow rate of the n-heptane-n-hexane-tetrahydrofuran is 700 L / h and the flow rate of water is 2100 L / h, the other conditions are the same as those in Example 3.

[0049] Example 5

[0050] In this embodiment, except that the flow rate of the n-heptane-n-hexane-tetrahydrofuran is 800 L / h and the flow rate of water is 2400 L / h, the other conditions are the same as those in Example 3.

[0051] Comparative Example 1

[0052] In this comparative example, except that the centrifugal extraction is replaced by countercurrent extraction, the other conditions are the same as those in Example 3.

[0053] Comparative Example 2

[0054] In this comparative example, except that the flow rate of water is 1320 L / h, the other conditions are the same as those in Example 3.

[0055] Comparative Example 3

[0056] In this comparative example, except that the flow rate of water is 2640 L / h, the other conditions are the same as those in Example 3.

[0057] In Examples 1-5 and Comparative Examples 1-4, the composition of the n-heptane-n-hexane-tetrahydrofuran mixed system is 10 wt% of n-heptane, 25 wt% of n-hexane, and 65 wt% of tetrahydrofuran. The purity of the finally obtained tetrahydrofuran was tested by gas chromatography, and the results are shown in Table 1.

[0058] Table 1

[0059]

[0060]

[0061] Although the purity of the tetrahydrofuran separated in Comparative Example 3 is improved compared with that in Example 3. The reason is that the amount of the extraction agent water in Comparative Example 3 is 40% higher than that in Example 3. However, its purity is only increased by 0.04%, and the economy is greatly reduced.

[0062] The applicant declares that the detailed structural features of the present invention are illustrated by the above embodiments, but the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvement to the present invention, the equivalent replacement of the components selected by the present invention, the addition of auxiliary components, the selection of specific methods, etc. all fall within the protection scope and the disclosure scope of the present invention.

[0063] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0064] In addition, it should be noted that, in the case of no contradiction, the various specific technical features described in the above specific embodiments can be combined in any appropriate manner. To avoid unnecessary repetition, the present invention will not separately describe various possible combination manners.

[0065] In addition, any combination can be made between various different embodiments of the present invention, as long as it does not violate the idea of the present invention, and it should also be regarded as the content disclosed by the present invention.

Claims

1. A method for separating tetrahydrofuran from a n - heptane - n - hexane - tetrahydrofuran mixed system, characterized in that, The method includes: Centrifugally extracting a n-heptane - n-hexane - tetrahydrofuran mixed system with water as the extractant to obtain a heavy-phase discharge; Rectifying the heavy-phase discharge to obtain a tetrahydrofuran - water azeotrope; Dehydrating the tetrahydrofuran - water azeotrope to obtain tetrahydrofuran.

2. The method according to claim 1, wherein The rotation speed of the centrifugal extraction is 500 - 1500 rpm.

3. The method according to claim 1 or 2, characterized in that The centrifugal extraction is at least a 4-stage continuous extraction.

4. The method according to any one of claims 1 to 3, characterized in that The flow rate ratio of the water to the n-heptane - n-hexane - tetrahydrofuran mixed system is 2.5 - 3.5:

1.

5. The method according to any one of claims 1 to 4, characterized in that, The light-phase discharge of the centrifugal extraction is n-heptane and / or n-hexane.

6. The method according to any one of claims 1-5, characterized in that, In the rectification, the pre-fraction at 60 - 70 °C is the tetrahydrofuran - water azeotrope.

7. The method according to any one of claims 1 to 6, characterized in that, The content of tetrahydrofuran in the tetrahydrofuran - water azeotrope is 90 - 99%.

8. The method according to any one of claims 1-7, characterized in that, The dehydration treatment is membrane dehydration treatment.

9. The method according to any one of claims 1-8, characterized in that, The water content of the tetrahydrofuran after the dehydration treatment is less than 0.5 wt%.

10. The method according to any one of claims 1-9, characterized in that, The method includes: Centrifugally extracting a n-heptane - n-hexane - tetrahydrofuran mixed system with water as the extractant, the centrifugal extraction is at least a 4-stage continuous extraction, the rotation speed is 500 - 1500 rpm, the flow rate ratio of the water to the n-heptane - n-hexane - tetrahydrofuran mixed system is 2.5 - 3.5:1, to obtain a heavy-phase discharge; Rectifying the heavy-phase discharge to obtain a tetrahydrofuran - water azeotrope, in the rectification, the pre-fraction at 60 - 70 °C is the tetrahydrofuran - water azeotrope, the content of tetrahydrofuran in the tetrahydrofuran - water azeotrope is 90 - 99%; Conducting membrane dehydration treatment on the tetrahydrofuran - water azeotrope to obtain tetrahydrofuran, the water content of the tetrahydrofuran after the dehydration treatment is less than 0.5 wt%.

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