Device for separating and recycling mixed liquid of acetonitrile, triethylamine and water

Abstract

The utility model relates to a device for separating and recycling mixed liquor of acetonitrile, triethylamine and water. The device comprises a first rectifying tower, a washing tank, membrane separation equipment and a second rectifying tower, wherein the top outlet of the first rectifying tower is connected with the inlet of the washing tank, the light-phase outlet of the washing tank is connected with the inlet of the second rectifying tower, and the bottom outlet of the first rectifying tower is connected with the inlet of the membrane separation equipment. A washing tank heavy-phase outlet is connected to a first rectifying tower inlet. A tower top outlet of the second rectifying tower is connected to a washing tank inlet. The device has the advantages that on the premise that a third-party component is not introduced, through rectification and membrane dehydration, azeotrope of acetonitrile, triethylamine and water is subjected to phase separation operation through the washing tank by utilizing the dissolvability of triethylamine, then triethylamine is used as a water-carrying agent, a mixture of triethylamine, acetonitrile and water is extracted from the tower top through secondary rectification, and the product quality is improved. Obtaining a triethylamine finished product from a tower kettle; as no third-party component is introduced, the purity of the recovered acetonitrile and triethylamine is higher, and no waste liquid exists.

Description

Technical Field

[0001] The utility model relates to the field of chemical separation and purification, in particular to a device for separating and recovering a mixed liquid of acetonitrile, triethylamine and water. Background Art

[0002] Acetonitrile is an excellent solvent with a wide range of uses. It is used in most fields such as pharmaceuticals, synthetic fibers, and petrochemicals. In particular, the demand for acetonitrile in the synthesis of medicines and pesticides has increased year by year.

[0003] Triethylamine is a low-chain fatty amine, slightly soluble in water. It is a common chemical intermediate and a common solvent in some reactions.

[0004] Acetonitrile and triethylamine are widely used in the fine chemical and pharmaceutical industries. For example, a large amount of acetonitrile and triethylamine mixed aqueous solution is produced during the production process of alanyl-glutamine. If the acetonitrile and triethylamine can be recovered, the resource utilization rate will be greatly improved and environmental pollution will be avoided.

[0005] However, the boiling point of acetonitrile is 81.48°C, the boiling point of triethylamine is 88.63°C, and the boiling point of water is 100°C. Under normal pressure, acetonitrile, triethylamine and water form acetonitrile-water, triethylamine-water, acetonitrile-triethylamine binary azeotrope and acetonitrile-triethylamine-water ternary azeotrope, which are difficult to separate by ordinary distillation methods.

[0006] In the existing public documents, the separation of acetonitrile and triethylamine is usually separated by extractive distillation or azeotropic distillation process, which requires the introduction of a third-party component---entrainer. Chinese patent CN106349107A discloses a method and device for separating acetonitrile-triethylamine mixture by heterogeneous azeotropic distillation, which discloses that n-hexane is used as an entrainer, is passed into the upper part of an azeotropic distillation tower, and a heterogeneous azeotrope is formed by n-hexane and acetonitrile to separate triethylamine and acetonitrile mixture. However, it is difficult to effectively evaluate the impact of the introduction of the third-party component on the pharmaceutical production process.

[0007] Therefore, it is necessary to design a separation and recovery device to achieve low energy consumption and high efficiency recovery of acetonitrile and triethylamine without introducing third-party substances. Summary of the invention

[0008] The utility model aims to design a separation and recovery device, which can realize low energy consumption and high efficiency recovery of acetonitrile and triethylamine without introducing third-party substances.

[0009] To achieve the purpose of the present invention, the technical solution is as follows:

[0010] A device for separating and recovering a mixed liquid of acetonitrile, triethylamine and water comprises: a first distillation tower, a water washing tank, a membrane separation device and a second distillation tower; wherein the top outlet of the first distillation tower is connected to the inlet of the water washing tank, the light phase outlet of the water washing tank is connected to the inlet of the second distillation tower, and the kettle outlet of the first distillation tower is connected to the inlet of the membrane separation device.

[0011] Furthermore, the heavy phase outlet of the water washing tank is connected to the inlet of the first distillation tower.

[0012] Furthermore, the top outlet of the second distillation tower is connected to the inlet of the water washing tank.

[0013] The device also includes a condenser, the top outlet of the first distillation tower is connected to the inlet of the condenser, and the outlet of the condenser is connected to the inlet of the water washing tank.

[0014] Furthermore, the membrane material used in the membrane separation equipment is a preferentially water-permeable membrane, selected from one or any two or any three or any four of a Na molecular sieve membrane, an organic polymer membrane, a hollow fiber membrane, and a composite membrane.

[0015] Further, the inlet of the first distillation tower is located in the tower; and / or the inlet of the second distillation tower is located in the tower.

[0016] The operating temperature of the water washing tank is 40-60°C, and the amount of water added during water washing is 0.5-1 times of the material produced from the top of the first distillation tower. The operating pressure of the first distillation tower is 0-0.1mPa; its top extraction temperature is 70-80°C, the reflux ratio is 0.5-5; the tower bottom temperature is 85-95°C. The operating pressure of the second distillation tower is 0-0.1mPa, its top extraction temperature is 80-90°C, the reflux ratio is 0.5-5; the tower bottom temperature is 90-105°C.

[0017] Compared with the prior art, the utility model has the following significant advantages:

[0018] 1. Without introducing any third-party components, by distillation and membrane dehydration, the solubility of triethylamine in water becomes worse as the temperature increases, and by phase separation in a water washing tank, the azeotrope of acetonitrile, triethylamine and water is secondary separated, and triethylamine is used as a water-carrying agent. A mixture of triethylamine, acetonitrile and water is extracted from the top of the tower by secondary distillation, and the finished triethylamine product is obtained in the bottom of the tower;

[0019] 2. Since no third-party components are introduced, the recovered acetonitrile and triethylamine are of higher purity and there is basically no waste liquid; the removed water can also be directly discharged without further separation and degradation;

[0020] 3. The device has simple process, high separation efficiency, good safety and equipment stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1The utility model is a schematic diagram of the structure of a device for separating and recovering a mixed liquid of acetonitrile, triethylamine and water.

[0022] Among them, 1 is the first distillation tower, 2 is the water washing tank, 3 is the membrane separation equipment, 4 is the second distillation tower, and 5 is the condenser. DETAILED DESCRIPTION

[0023] The transportation of each material in this embodiment can be controlled by pipelines, pumps, valves, and control systems, and the temperature of the material can be adjusted by various heaters, heat exchangers, and other equipment.

[0024] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0025] The mixed solution of acetonitrile, triethylamine and water comprises the following components and their mass percentages: 60-90 wt.% of acetonitrile, 10-30 wt.% of triethylamine, and 10-20 wt.% of water.

[0026] A device for separating and recovering a mixed liquid of acetonitrile, triethylamine and water, comprising: a first distillation tower 1, a water washing tank 2, a membrane separation device 3 and a second distillation tower 4; wherein the top outlet of the first distillation tower 1 is connected to the inlet of the water washing tank 2, the light phase outlet of the water washing tank 2 is connected to the inlet of the second distillation tower 4, and the bottom outlet of the first distillation tower 1 is connected to the inlet of the membrane separation device 3. Furthermore, the heavy phase outlet of the water washing tank 2 is connected to the inlet of the first distillation tower 1. The top outlet of the second distillation tower 4 is connected to the inlet of the water washing tank 2.

[0027] The first distillation tower 1 is used for preliminary separation and recovery of acetonitrile and triethylamine. The water washing tank 2 is used for washing the acetonitrile, triethylamine and water azeotrope produced from the top of the first distillation tower 1 with water, and the triethylamine and acetonitrile are separated again by using the characteristic that the higher the temperature of triethylamine, the worse its solubility in water. The membrane separation device 3 is used for separating the bottom liquid of the first distillation tower 1 into acetonitrile and water. The second distillation tower 4 is used for further separation of triethylamine and water.

[0028] As a specific embodiment, the device for separating and recovering a mixture of acetonitrile, triethylamine and water also includes a condenser 5, the top outlet of the first distillation tower 1 is connected to the condenser inlet, and the condenser outlet is connected to the inlet of the water washing tank 2.

[0029] The membrane material selected for the membrane separation device 3 is a preferentially water-permeable membrane, which can be selected from one of Na molecular sieve membranes, organic polymer membranes, hollow fiber membranes, and composite membranes, or a combination of any two or any three or more thereof.

[0030] The first distillation tower 1 and the second distillation tower 4 can be plate towers or packed towers. When the first distillation tower and the second distillation tower are selected from plate towers; wherein, the theoretical number of plates of the first distillation tower 1 is 42; the theoretical number of plates of the second distillation tower 4 is 24. The inlet of the first distillation tower 1 or the second distillation tower 4 is located in the tower. As a specific embodiment, the feed inlet position of the first distillation tower 1 can be the 20th plate from the bottom to the top. The feed inlet position of the second distillation tower 4 is the 8th plate from the bottom to the top.

[0031] like Figure 1 As shown, the process flow of the device is specifically described:

[0032] The first step: transport the mixed liquid of acetonitrile, triethylamine and water to the first distillation tower 1, and perform atmospheric distillation. The operating pressure of the first distillation tower 1 is 0-0.1 mPa (gauge pressure); the top extraction temperature is 70-80°C, the reflux ratio is 0.5-5; the bottom temperature is 85-95°C. The azeotropic mixture of acetonitrile, triethylamine and water (acetonitrile 5-15wt.%, triethylamine 80-90wt.%, water 5-15wt.%) is extracted from the top of the first distillation tower 1 and collected in the washing tank 2; when no triethylamine is detected at the top of the tower, the bottom liquid of the first distillation tower 1 enters the membrane separation device 3 for dehydration. The operating temperature of the membrane separation device 3 is 85-130°C, and the pressure is 0.1-0.25 mPa (gauge pressure).

[0033] Step 2: The azeotrope extracted from the top of the first distillation tower 1 enters the washing tank 2 for washing and stratification. By utilizing the characteristic that the higher the temperature of triethylamine is, the worse its solubility in water is, the light phase of triethylamine almost free of acetonitrile is obtained in the upper layer, and the heavy phase of the mixture of acetonitrile, triethylamine and water is obtained in the lower layer. The amount of water added during washing is 0.5 to 1 times of the azeotrope extracted from the top of the first distillation tower 1, and the temperature of the washing tank is controlled to be 40 to 60°C during washing. After washing and stratification, the composition of the upper light phase is: 95 to 99 wt.% of triethylamine, 0.1 to 1 wt.% of acetonitrile, and 1 to 5 wt.% of water; the composition of the lower heavy phase is: 10 to 25 wt.% of triethylamine, 10 to 25 wt.% of acetonitrile, and 50 to 80 wt.% of water.

[0034] The third step: the light phase obtained in the washing tank 2 is transferred to the second distillation tower 4 for atmospheric distillation. The triethylamine can form corresponding azeotropes with acetonitrile and water respectively. The triethylamine is used as a water-carrying agent to extract a mixture of triethylamine, acetonitrile and water from the top of the tower, and transferred to the inlet of the washing tank 2 to continue to recover the acetonitrile and triethylamine therein; and when the water content of the second distillation tower kettle is detected to be qualified (reaching below 200ppm), the tower kettle directly extracts qualified triethylamine finished product. The operating pressure of the second distillation tower 4 is 0-0.1mPa, the top extraction temperature is 80-90℃, the reflux ratio is 0.5-5; the tower kettle temperature is 90-105℃.

[0035] The distillation tower in this embodiment includes not only the tower body, but also related supporting equipment and instrument systems such as pumps, pipelines, valves, control systems, etc. configured for the distillation tower body in order to achieve distillation. For example, the top of the first distillation tower and the bottom of the second distillation tower are equipped with an online moisture meter for detecting the moisture content.

Claims

1. A device for separating and recovering a mixed solution of acetonitrile, triethylamine and water, characterized in that: The invention comprises a first distillation tower (1), a water washing tank (2), a membrane separation device (3) and a second distillation tower (4); wherein the top outlet of the first distillation tower (1) is connected to the inlet of the water washing tank (2), the light phase outlet of the water washing tank (2) is connected to the inlet of the second distillation tower (4), the bottom outlet of the first distillation tower (1) is connected to the inlet of the membrane separation device (3); the heavy phase outlet of the water washing tank (2) is connected to the inlet of the first distillation tower (1); and the top outlet of the second distillation tower (4) is connected to the inlet of the water washing tank (2).

2. The device for separating and recovering acetonitrile, a mixed solution of triethylamine and water according to claim 1, is characterized in that: The device also includes a condenser (5), the top outlet of the first distillation tower (1) is connected to the inlet of the condenser, and the outlet of the condenser is connected to the inlet of the water washing tank (2).

3. The device for separating and recovering acetonitrile, a mixed solution of triethylamine and water according to claim 1, is characterized in that: The membrane material selected for the membrane separation device (3) is a preferentially water-permeable membrane, which is selected from one or any two or any three or any four of a Na molecular sieve membrane, an organic polymer membrane, a hollow fiber membrane, and a composite membrane.

4. The device for separating and recovering acetonitrile, a mixed solution of triethylamine and water according to claim 1, characterized in that: The inlet of the first distillation tower (1) is located in the tower; and / or the inlet of the second distillation tower (4) is located in the tower.

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