A refining apparatus and method for nitrogen-containing solvent precursors and applications

Abstract

The application discloses a refining device and method of nitrogen-containing solvent precursor and application. The refining method takes acetic amide intermediate product of methyl acetate two-step ammonia dehydration for preparing acetonitrile as a separation raw material, and after the steps of raw material recovery, azeotrope breaking and refining, and three-waste separation, acetic amide main product, acetonitrile by-product and recycled unreacted raw material are obtained, and trace impurities are dissolved by self-produced wastewater to avoid the discharge of polluting gas. The refining method is environment-friendly and suitable for industrialized large-scale continuous operation.

Description

TECHNICAL FIELD

[0001] The present application relates to a refining device and method of nitrogen-containing solvent precursor and application, belonging to the field of chemical technology. BACKGROUND

[0002] Acetonitrile is a colorless transparent liquid compound with sweet taste, which is an important fine chemical raw material, widely used in the synthesis of pharmaceutical, pesticide chemical intermediates, and also a good performance organic solvent. At present, the mature acetonitrile synthesis route has only two kinds of acrylonitrile by-product method and ammoniation dehydration method of acetic acid. The former acetonitrile production is severely restricted by acrylonitrile production capacity, and the latter raw material has strong corrosion, and the profit space is sharply compressed due to the influence of raw material price. New acetonitrile preparation route is basically in the laboratory research stage, and no industrialization exploration is carried out, so it is necessary to continue to study.

[0003] The ammoniation dehydration process of methyl acetate two-step method is a low-cost and high-product-purity acetonitrile preparation method. The industrialization difficulty of this method lies in the separation and refining process of the first step of preparing acetamide from methyl acetate ammoniation. SUMMARY

[0004] According to one aspect of the present application, a refining method of nitrogen-containing solvent precursor is provided, comprising the following steps:

[0005] a) passing the ammoniation product into the light-removing tower, separating the condensate, obtaining mixture I containing dimethyl ether at the top, obtaining ammonia gas at the side line, and obtaining intermediate product I at the bottom;

[0006] b) passing the intermediate product I into the methanol tower, azeotropically separating I, obtaining mixture II containing methyl acetate and methanol at the top, and obtaining intermediate product II at the bottom;

[0007] c) passing the intermediate product II and water into the acetonitrile tower, azeotropically separating II to obtain acetonitrile and mixture III containing acetamide and water;

[0008] d) passing the mixture III into the product tower, separating, obtaining water at the top, and obtaining acetamide at the bottom;

[0009] The molar composition of the ammoniation product is:

[0010] Methyl acetate 3.5-7.5%,

[0011] Ammonia 70-85%,

[0012] Acetonitrile 0.3-2.5%,

[0013] Acetamide 0.4-8.5%,

[0014] Methanol 2.5-7.5%,

[0015] dimethyl ether 0.001-0.05%,

[0016] water 0.5-3.5%.

[0017] As a specific refining process, the ammoniated product is first fed into the light-removing column 1 to separate dimethyl ether impurities and a small amount of ammonia at the top, and then sent to the absorption tank 5, where it is mixed with waste water for absorption and then discharged. The ammonia gas is taken from the side line of the light-removing column 1 and used as a circulating raw material. The material obtained at the bottom of the column is sent to the methanol column 2. The methanol column 2 breaks part of the azeotropic system by pressure design, separates the mixture of unreacted methyl acetate and methanol at the top, and sends it to the esterification unit to produce reaction raw materials. The heavy components containing water and acetyl are obtained at the bottom of the column. The material at the bottom of the acetonitrile column 3 is separated in the product column 4 to obtain waste water and acetamide, and the waste water is sent to the absorption tank 5 and the bottom of the acetonitrile column 3, respectively.

[0018] Optionally, in step a), the mixture I is fed into an absorption tank and mixed with water.

[0019] Optionally, in step b), the mixture II is fed into an esterification unit for esterification reaction.

[0020] Optionally, in step d), the water obtained at the top is fed into an acetonitrile column and an absorption tank, respectively.

[0021] Optionally, in step a), the reflux ratio of the light-removing column is 200-1000, the theoretical plate number is 10-80, the top temperature is -20-60°C, and the operating pressure is 200-900 kPaA.

[0022] Optionally, in step b), the reflux ratio of the methanol column is 0.1-10, the theoretical plate number is 10-80, the top temperature is 60-150°C, and the operating pressure is 300-800 kPaA.

[0023] Optionally, in step c), the reflux ratio of the acetonitrile column is 0.1-60, the theoretical plate number is 10-80, the top pressure is -60-20°C, and the operating pressure is 0-20 kPaA.

[0024] Optionally, in step d), the reflux ratio of the product column is 0.01-20, the theoretical plate number is 10-80, the top temperature is 10-60°C, and the operating pressure is 0-200 kPaA.

[0025] According to still another aspect of the present application, there is provided a refining device for a nitrogen-containing solvent precursor, comprising a light-removing column, a methanol column, an acetonitrile column, a product column, an absorption tank,

[0026] The overhead outlet of the light-removing column is connected with the absorption tank, the ammonia gas outlet of the light-removing column is connected with the reaction unit, and the bottom outlet of the light-removing column is connected with the feed inlet of the methanol column.

[0027] The overhead outlet of the methanol column is connected with the esterification unit, and the bottom outlet of the methanol column is connected with the feed inlet of the acetonitrile column.

[0028] The overhead outlet of the acetonitrile column is connected with the acetonitrile collection unit, and the bottom outlet of the acetonitrile column is connected with the feed inlet of the product column.

[0029] The bottom outlet of the product column is connected with the acetamide collection unit, and the water vapor outlet of the product column is connected with the absorption tank and the acetonitrile column respectively.

[0030] Optionally, the absorption tank is a gas-liquid mixer.

[0031] Optionally, the gas-liquid mixer comprises a two-phase mixing pipeline of a gas-phase inlet inserted into an adiabatic container below the liquid surface or an injection nozzle.

[0032] According to another aspect of the present application, there is provided a refining separation method of the precursor acetamide for acetonitrile produced by methyl acetate ammoniation, which uses the above refining device and the above refining method for refining separation.

[0033] The present application can produce the following beneficial effects:

[0034] The refining method provided by the present application can obtain the main product acetamide, the by-product acetonitrile, and the unreacted raw material for recycling after the steps of raw material recovery, azeotrope breaking refining, and three-waste separation, and can dissolve trace impurities and non-condensable gas by using self-produced wastewater, thereby avoiding the discharge of polluting gas. The process is continuous, and can be used for the separation and refining of the precursor acetamide for acetonitrile produced by methyl acetate ammoniation, is environmentally friendly, and is suitable for industrialized large-scale continuous operation. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 FIG. 1 is a schematic diagram of a separation method of a liquid-phase ammonia-containing mixed product according to Embodiment 1 of the present application; 1, light-removing column, 2, methanol column, 3, acetonitrile column, 4, product column, 5, absorption tank. DETAILED DESCRIPTION

[0036] The present application will be described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0037] According to one embodiment of the present application, the separation of the raw material with a molar composition of 3.5-7.5% methyl acetate, 70-85% ammonia, 0.3-2.5% acetonitrile, 0.4-8.5% acetamide, 2.5-7.5% methanol, 0.5-3.5% water, and 0.001-0.05% dimethyl ether is refined and separated.

[0038] Figure 1 The separation method of the liquid phase ammonia-containing mixed product of the present application is shown in the schematic diagram, which comprises the following steps:

[0039] 1) The raw material is first fed into the light-removing column 1, and the dimethyl ether impurities are separated at the top of the column and entrain a small amount of ammonia, which is fed into the absorption tank 5 and mixed with the tank waste water for absorption and then discharged; the ammonia gas is taken from the side line of the light-removing column 1 and used as a circulating raw material; the material obtained at the bottom of the light-removing column 1 is fed into the methanol column 2;

[0040] 2) The mixture of unreacted methyl acetate and methanol is separated at the top of the methanol column 2 and fed into the esterification unit to produce the reaction raw material, and the heavy component containing water and acetyl obtained at the bottom of the column is fed into the acetonitrile column 3;

[0041] 3) The acetonitrile column 3 breaks the remaining azeotropic system by pressure design, and part of the circulating waste water is injected at the bottom of the column to avoid the crystallization of acetamide, and the acetonitrile byproduct is obtained at the top of the column, and the heavy component containing water and acetyl is obtained at the bottom of the column;

[0042] 4) The material at the bottom of the acetonitrile column 3 is separated in the product column 4 to obtain waste water and acetamide product, and the waste water is fed into the absorption tank 5 and the acetonitrile column 3, respectively.

[0043] Example 1

[0044] The separated raw material (mole composition: methyl acetate 5.44%, ammonia 82.46%, acetonitrile 1.10%, acetamide 4.40%, methanol 5.49%, water 1.11%, dimethyl ether 0.0049%) is first fed into the light-removing column 1, which has 30 theoretical plates, a top pressure of 600 kPaA, a top temperature of 3°C, and a reflux ratio of 600. The dimethyl ether with a mole content of 28.19% is separated at the top of the column 1 and is fed into the absorption tank 5, where it is mixed with waste water and discharged after absorption. Ammonia with a mole concentration of 99.4% is collected at the 14th theoretical plate and can be used as a circulating raw material. The material at the bottom of the column 1 is fed into the methanol column 2, which has 40 theoretical plates, a top pressure of 665 kPaA, a top temperature of 114°C, and a reflux ratio of 7. The mixture of methanol and methyl acetate is separated at the top of the column 2 and is fed into the esterification device for synthesis. The heavy components containing water and acetic acid are obtained at the bottom of the column 2 and are fed into the acetonitrile column 3. The column 3 has 50 theoretical plates, a top pressure of 1 kPaA, a top temperature of -20°C, and a reflux ratio of 30. Waste water is injected at the bottom of the column 3. Acetonitrile is obtained at the top of the column 3, and the heavy components containing water and acetic acid are obtained at the bottom of the column 3. The material at the bottom of the column 3 is fed into the product column 4, which has 30 theoretical plates, a top pressure of 10 kPaA, a top temperature of 46°C, and a reflux ratio of 1. The material is separated in the column 4 to obtain waste water and the target product acetamide with a mole concentration of 99.82%. The waste water is fed into the absorption tank 5 and the column 3, respectively.

[0045] The above is only a few embodiments of the present application, and does not limit the present application in any form. Although the preferred embodiments are disclosed above, the present application is not limited thereto. Any person skilled in the art can make some changes or modifications to the above disclosed technical contents without departing from the scope of the present application, and such changes or modifications are equivalent to equivalent embodiments and are within the scope of the present application.

Claims

1. A method of refining a nitrogen-containing solvent precursor, characterized by, The process comprises the following steps: a) passing the ammoniated product into a light-removing column, fractionating, obtaining mixture I containing dimethyl ether at the top, obtaining ammonia gas at the side line, and obtaining intermediate product I at the bottom; b) passing the intermediate product I into a methanol column, azeotropically separating, obtaining mixture II containing methyl acetate and methanol at the top, and obtaining intermediate product II at the bottom; c) passing the intermediate product II and water into an acetonitrile column, azeotropically separating, obtaining acetonitrile by-product at the top, and obtaining mixture III containing water and acetamide at the bottom; d) passing the mixture III into a product column, separating, obtaining water at the top, and obtaining acetamide at the bottom; The molar composition of the ammoniated product is: methyl acetate 3.5~7.5%, ammonia 70~85%, acetonitrile 0.3~2.5%, acetamide 0.4~8.5%, methanol 2.5~7.5%, dimethyl ether 0.001~0.05%, water 0.5~3.5%.

2. The refining method according to claim 1, characterized by, In step a), the mixture I is mixed with water in an absorption tank.

3. The refining method according to claim 1, characterized by, In step b), the mixture II is passed into an esterification unit for esterification reaction.

4. The refining method according to claim 1, characterized by, In step d), the water obtained at the top is passed into an acetonitrile column and an absorption tank, respectively.

5. The method of claim 1, wherein the refining is performed by a method comprising: In step a), the reflux ratio of the light-removing column is 200~1000, the theoretical plate number is 10~80, the top temperature is -20~60℃, and the operating pressure is 200~900 kPaA.

6. The method of claim 1, wherein the refining is performed by a method comprising: In step b), the reflux ratio of the methanol column is 0.1~10, the theoretical plate number is 10~80, the top temperature is 60~150℃, and the operating pressure is 300~800 kPaA.

7. The method of claim 1, wherein the refining is performed by a method comprising: In step c), the reflux ratio of the acetonitrile column is 0.1~60, the theoretical plate number is 10~80, the top temperature is -60~20℃, and the operating pressure is 0~20 kPaA.

8. The method of claim 1, wherein the refining is performed by a method comprising: In step d), the reflux ratio of the product column is 0.01~20, the theoretical plate number is 10~80, the top temperature is 10~60℃, and the operating pressure is 0~200 kPaA.

9. A nitrogen-containing solvent precursor refining apparatus for carrying out the refining method according to any one of claims 1 to 8, characterized by, The process comprises a light-removing column, a methanol column, an acetonitrile column, a product column, and an absorption tank, the top outlet of the light-removing column is connected with the absorption tank, the ammonia gas outlet of the light-removing column is connected with a reaction unit, and the bottom outlet of the light-removing column is connected with the feeding port of the methanol column; the top outlet of the methanol column is connected with an esterification unit, and the bottom outlet of the methanol column is connected with the feeding port of the acetonitrile column; the top outlet of the acetonitrile column is connected with an acetonitrile collection unit, and the bottom outlet of the acetonitrile column is connected with the feeding port of the product column; the bottom outlet of the product column is connected with an acetamide collection unit, and the water vapor outlet of the product column is connected with the absorption tank and the acetonitrile column, respectively.

10. The finishing apparatus of claim 9, wherein The absorption tank is a gas-liquid mixer.

11. The finishing apparatus of claim 10, wherein The gas-liquid mixer comprises a two-phase mixing pipeline of a gas phase inlet inserted into a liquid level below an adiabatic container or an internal injection nozzle.

12. A method for the purification and separation of the precursor acetamide for the amination of methyl acetate to acetonitrile, characterized in that The refining separation method is selected from the refining method of any one of claims 1 to 8; and the device of the refining separation method is selected from the refining device of any one of claims 9 to 11.

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