Refining device of nitrogen-containing solvent precursor and refining method and application thereof

Abstract

The invention discloses a refining device of a nitrogen-containing solvent precursor and a refining method and application thereof. The refining method comprises the following steps: by taking a liquid-phase material obtained after cryogenic separation of a gas-phase mixture obtained by ammoniation reaction as a raw material, carrying out segregation side-stream rectification, component coarse separation, three-waste separation and differential pressure separation to obtain an acetonitrile main product, an acetamide byproduct and recycled unreacted raw materials; and trace impurity non-condensable gas is dissolved at low temperature through self-produced wastewater, so that pollution gas is prevented from being discharged. The method can be used for separating and refining the liquid-phase reaction product of acetonitrile prepared by ammoniating methyl acetate, and is simple in process, environment-friendly, easy to operate and suitable for industrial large-scale continuous production.

Description

Technical Field

[0001] The present application relates to a refining device for a nitrogen-containing solvent precursor, a refining method and an application thereof, and belongs to the technical field of chemical engineering. Background Art

[0002] Acetonitrile is a colorless, transparent, sweet-tasting liquid compound. It is an important fine chemical raw material and is widely used in the synthesis of pharmaceutical and pesticide chemical intermediates. It is also an organic solvent with good performance. At present, there are only two mature acetonitrile synthesis routes: the acrylonitrile byproduct method and the acetic acid ammoniation dehydration method. The acetonitrile production of the former is severely restricted by the acrylonitrile production capacity, and the raw materials of the latter are highly corrosive. At the same time, the profit margin is sharply compressed due to the influence of the raw material price. The new acetonitrile preparation routes are basically in the laboratory research stage and have not been explored for industrialization. Therefore, there is a need for continuous research.

[0003] The process of ammoniation and dehydration of methyl acetate is a low-cost, high-purity method for producing acetonitrile. The difficulty in industrializing this method lies in the separation of raw materials and non-condensable gas phase impurities and the refining process of the acetonitrile product. Summary of the invention

[0004] In order to overcome the problem of difficulty in separating raw materials from non-condensable gas phase impurities in the reaction process of ammoniation of methyl acetate to acetonitrile, the present application provides a method for refining the crude liquid product of the method, which has a simple process, is environmentally friendly, is easy to operate, and is suitable for industrial large-scale continuous production.

[0005] According to one aspect of the present application, a method for refining a nitrogen-containing solvent precursor is provided, comprising the following steps:

[0006] A. The ammoniation product is passed into a deamination tower for fractional condensation to obtain material I containing dimethyl ether at the top of the tower, ammonia gas at the side line, and intermediate product I at the bottom of the tower;

[0007] B. Passing the intermediate product I into a light-removing tower, operating pressure, obtaining material II containing methyl acetate, methanol and acetonitrile at the top of the tower, obtaining a light-removing product at the bottom of the tower, and passing the dehydrogenation product into a wastewater tower, performing vacuum distillation, and obtaining an acetamide product at the bottom of the tower;

[0008] C. Passing the material II into a deesterification tower, performing full condensation and rectification, obtaining material III containing methyl acetate and methanol at the top of the tower, and obtaining an intermediate product II containing acetonitrile and methanol at the bottom of the tower;

[0009] D. Passing the intermediate product II into a high-pressure tower and pressurizing it to obtain material IV containing methanol and acetonitrile at the top of the tower and an acetonitrile product at the bottom of the tower;

[0010] E. Passing the material IV into a low-pressure tower, releasing the pressure, and passing the material V containing methanol and acetonitrile at the top of the tower into the high-pressure tower to obtain a methanol product at the bottom of the tower;

[0011] The molar composition of the amination product is:

[0012] Methyl acetate 0.005-0.2%;

[0013] Ammonia 30-80%;

[0014] Acetonitrile 5-25%;

[0015] Acetamide 0.1~1.0%;

[0016] Methanol 3-30%;

[0017] Dimethyl ether 0.001~1.5%;

[0018] Water 5-25%.

[0019] Optionally, in step A, the material I is passed into an absorption tank and mixed with water.

[0020] Optionally, in step B, the water vapor obtained at the top of the wastewater tower is condensed in a wastewater cooler and then passed into the absorption tank.

[0021] Optionally, in step A, the reflux ratio of the deamination tower is 200 to 1000, the number of theoretical plates is 10 to 80, the top temperature is -20 to 60°C, and the operating pressure is 200 to 900 kPaA.

[0022] Optionally, in step B, the reflux ratio of the light-removal tower is 0.1 to 10, the number of theoretical plates is 10 to 80, the top temperature is -40 to 80°C, and the operating pressure is 0.01 to 10 kPaA.

[0023] Optionally, the reflux ratio of the wastewater tower is 0.1-10, the number of theoretical plates is 10-80, the top temperature is 10-60° C., and the operating pressure is 0.01-200 kPaA.

[0024] Optionally, in step C, the reflux ratio of the deesterification tower is 100-900, the number of theoretical plates is 10-80, the top temperature is 20-80° C., and the operating pressure is 0-200 kPaA.

[0025] Optionally, in step D, the reflux ratio of the high-pressure tower is 0.1 to 30, the number of theoretical plates is 10 to 80, the tower top temperature is 50 to 150° C., and the operating pressure is 150 to 600 kPaA.

[0026] Optionally, in step E, the reflux ratio of the low-pressure tower is 0.1 to 30, the number of theoretical plates is 10 to 80, the tower top temperature is 30 to 150° C., and the operating pressure is 20 to 300 kPaA.

[0027] Optionally, the operating pressure of the absorption tank is 1-300 kPaA, and the operating temperature is 1-40°C.

[0028] Optionally, the operating temperature of the wastewater cooler is 1-40°C.

[0029] According to another aspect of the present application, a refining device for a nitrogen-containing solvent precursor is provided, comprising a deamination tower, a lightness removal tower, a wastewater tower, a deesterification tower, a high-pressure tower and a low-pressure tower.

[0030] The top outlet of the deamination tower is connected to the absorption tank, the ammonia outlet of the deamination tower is connected to the reaction unit, and the bottom outlet of the deamination tower is connected to the material inlet of the lightness removal tower;

[0031] The top outlet of the light-removing tower is connected to the material inlet of the deesterification tower, and the bottom outlet of the light-removing tower is connected to the wastewater tower;

[0032] The bottom outlet of the wastewater tower is connected to the acetamide recovery unit;

[0033] The top outlet of the deesterification tower is connected to the methyl acetate recovery unit, and the bottom outlet of the deesterification tower is connected to the material inlet of the high-pressure tower;

[0034] The top outlet of the high-pressure tower is connected to the material inlet of the low-pressure tower, and the bottom outlet of the high-pressure tower is connected to the acetonitrile recovery unit;

[0035] The top outlet of the low-pressure tower is connected to the feed inlet of the high-pressure tower, and the bottom outlet of the low-pressure tower is connected to the methanol recovery unit.

[0036] Optionally, the top outlet of the wastewater tower is connected to the absorption tank, and a wastewater cooler is provided between the top outlet of the wastewater tower and the absorption tank.

[0037] Optionally, the absorption tank is a gas-liquid mixer.

[0038] Optionally, the gas-liquid mixer comprises a two-phase mixing pipe with a gas phase inlet inserted into an insulated container or an internal injection nozzle below the liquid surface.

[0039] According to another aspect of the present application, a method for separating and refining a liquid phase reaction product of ammoniation of methyl acetate to acetonitrile is provided, wherein the separation and refining method is selected from the above-mentioned refining method.

[0040] The beneficial effects of this application include:

[0041] The method for refining the nitrogen-containing solvent precursor provided in the present application has a continuous process and can be used for separating and refining the liquid phase reaction product of the amination of methyl acetate to acetonitrile. The process is simple, environmentally friendly, easy to operate, and suitable for industrial large-scale continuous production. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is a schematic diagram of a method for purifying a nitrogen-containing solvent precursor according to the present application.

[0043] 1. Deamination tower, 2. Delight tower, 3. Wastewater tower, 4. Deesterification tower, 5. High-pressure tower, 6. Low-pressure tower, 7. Wastewater cooler, 8. Absorption tank. DETAILED DESCRIPTION

[0044] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0045] Example 1

[0046] The separated raw materials (molar composition is 0.05% methyl acetate, 54.09% ammonia, 14.61% acetonitrile, 0.91% acetamide, 15.34% methanol, 14.82% water, and 0.06% dimethyl ether) are first sent to the deamination tower 1. The top pressure of the deamination tower 1 is 700 kPaA, the top temperature is 9°C, 30 theoretical plates are set, and the reflux ratio is 700. Waste gas with a molar content of 19.90% of dimethyl ether is separated at the top of the deamination tower 1 and sent to the absorption tank 8, where it is adiabatically mixed with waste water for absorption and then discharged. Ammonia with a molar concentration of 99.97% is extracted on the 8th theoretical plate of the deamination tower 1 and can be continuously used in the reaction unit as a circulating raw material. The material obtained at the bottom of the deamination tower 1 is sent to the light removal tower 2. The top pressure of the light removal tower 2 is 1.5 kPaA, the top temperature is -18°C, 30 theoretical plates are set, and the reflux ratio is 3. A mixture containing methyl acetate, methanol and acetonitrile is separated at the top of the light removal tower 2 and sent to the deesterification tower 4. The light removal material obtained at the bottom of the light removal tower 2 is sent to the wastewater tower 3. The top pressure of the deesterification tower 4 is 109 kPaA, the top temperature is 56°C, 60 theoretical plates are set, and the reflux ratio is 600. The impurity oil containing methyl acetate and methanol is separated at the top of the deesterification tower 4 and transported to the methyl acetate recovery unit. The methanol and acetonitrile mixture is obtained at the bottom of the deesterification tower 4 and sent to the high-pressure tower 5. The top pressure of high-pressure tower 5 is 300kPaA, the top temperature is 95℃, 50 theoretical plates are set, and the reflux ratio is 10. Through distillation separation, high-pressure tower 5 obtains methanol-acetonitrile azeotrope at the top of the tower and sends it to low-pressure tower 6. High-pressure tower 5 obtains acetonitrile with a molar purity of 99.98% at the bottom of the tower and transports it to the acetonitrile recovery unit. The top pressure of low-pressure tower 6 is 110kPaA, the top temperature is 66℃, 50 theoretical plates are set, and the reflux ratio is 15. Low-pressure tower 6 obtains methanol / acetonitrile azeotrope at the top of the tower and sends it back to high-pressure tower 5 for separation. Low-pressure tower 6 obtains methanol with a molar purity of 99.96% at the bottom of the tower and transports it to the methanol mobile phone unit. Wastewater tower 3 receives the light removal product from the bottom of light removal tower 2, with a top pressure of 1.5kPaA, a top temperature of 16℃, 40 theoretical plates, and a reflux ratio of 0.6. Wastewater is obtained at the top of the wastewater tower 3, cooled to 10°C by a wastewater cooler 7, and then sent to an absorption tank 8. At the bottom of the absorption tank 8, by-product acetamide with a molar purity of 99.92% is obtained.

[0047] The above are only a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for purifying a nitrogen-containing solvent precursor, characterized in that: The following steps are involved: A. The ammoniation product is passed into a deamination tower for fractional condensation to obtain material I containing dimethyl ether at the top of the tower, ammonia gas at the side line, and intermediate product I at the bottom of the tower; B. Passing the intermediate product I into a light-removing tower, operating pressure, obtaining material II containing methyl acetate, methanol and acetonitrile at the top of the tower, obtaining a light-removing product at the bottom of the tower, and passing the dehydrogenation product into a wastewater tower, performing vacuum distillation, and obtaining an acetamide product at the bottom of the tower; C. Passing the material II into a deesterification tower, performing full condensation and rectification, obtaining material III containing methyl acetate and methanol at the top of the tower, and obtaining an intermediate product II containing acetonitrile and methanol at the bottom of the tower; D. Passing the intermediate product II into a high-pressure tower and pressurizing it to obtain material IV containing methanol and acetonitrile at the top of the tower and an acetonitrile product at the bottom of the tower; E. Passing the material IV into a low-pressure tower, releasing the pressure, and passing the material V containing methanol and acetonitrile at the top of the tower into the high-pressure tower to obtain a methanol product at the bottom of the tower; The molar composition of the amination product is: Methyl acetate 0.005-0.2%; Ammonia 30-80%; Acetonitrile 5-25%; Acetamide 0.1~1.0%; Methanol 3-30%; Dimethyl ether 0.001~1.5%; Water 5-25%.

2. The refining method according to claim 1, characterized in that In step A, the material I is passed into an absorption tank and mixed with water; Preferably, in step B, the water vapor obtained at the top of the wastewater tower is condensed in a wastewater cooler and then passed into the absorption tank.

3. The refining method according to claim 1, characterized in that: In step A, the reflux ratio of the deamination tower is 200-1000, the number of theoretical plates is 10-80, the top temperature is -20-60°C, DD230254I-DL The operating pressure is 200~900kPaA.

4. The refining method according to claim 1, characterized in that: In step B, the reflux ratio of the light-removal tower is 0.1 to 10, the number of theoretical plates is 10 to 80, the tower top temperature is -40 to 80°C, and the operating pressure is 0.01 to 10 kPaA; Preferably, the reflux ratio of the wastewater tower is 0.1-10, the number of theoretical plates is 10-80, the tower top temperature is 10-60° C., and the operating pressure is 0.01-200 kPaA.

5. The purification method according to claim 1, characterized in that: In step C, the reflux ratio of the deesterification tower is 100-900, the number of theoretical plates is 10-80, the top temperature is 20-80° C., and the operating pressure is 0-200 kPaA.

6. The purification method according to claim 1, characterized in that: In step D, the reflux ratio of the high-pressure tower is 0.1-30, the number of theoretical plates is 10-80, the tower top temperature is 50-150° C., and the operating pressure is 150-600 kPaA; Preferably, in step E, the reflux ratio of the low-pressure tower is 0.1-30, the number of theoretical plates is 10-80, the tower top temperature is 30-150° C., and the operating pressure is 20-300 kPaA.

7. The purification method according to claim 2, characterized in that: The operating pressure of the absorption tank is 1-300 kPaA, and the operating temperature is 1-40°C; Preferably, the operating temperature of the wastewater cooler is 1-40°C.

8. Use of a refining device for a nitrogen-containing solvent precursor in the refining method according to any one of claims 1 to 7, characterized in that: Including deamination tower, delight tower, wastewater tower, deesterification tower, high-pressure tower and low-pressure tower, The top outlet of the deamination tower is connected to the absorption tank, the ammonia outlet of the deamination tower is connected to the reaction unit, and the bottom outlet of the deamination tower is connected to the material inlet of the lightness removal tower; The top outlet of the light-removing tower is connected to the material inlet of the deesterification tower, and the bottom outlet of the light-removing tower is connected to the wastewater tower; The bottom outlet of the wastewater tower is connected to the acetamide recovery unit; DD230254I-DL The top outlet of the deesterification tower is connected to the methyl acetate recovery unit, and the bottom outlet of the deesterification tower is connected to the material inlet of the high-pressure tower; The top outlet of the high-pressure tower is connected to the material inlet of the low-pressure tower, and the bottom outlet of the high-pressure tower is connected to the acetonitrile recovery unit; The top outlet of the low-pressure tower is connected to the feed inlet of the high-pressure tower, and the bottom outlet of the low-pressure tower is connected to the methanol recovery unit.

9. The use according to claim 8, characterized in that: The top outlet of the wastewater tower is connected to the absorption tank, and a wastewater cooler is provided between the top outlet of the wastewater tower and the absorption tank; Preferably, the absorption tank is a gas-liquid mixer; Preferably, the gas-liquid mixer comprises a two-phase mixing pipe with a gas phase inlet inserted into an insulated container or an internal injection nozzle below the liquid surface.

10. A method for separating and refining the liquid phase reaction product of ammoniation of methyl acetate to acetonitrile, characterized in that: The separation and purification method is selected from the purification method according to any one of claims 1 to 7.

Images