CN113501770B - Acetonitrile refining method - Google Patents

Acetonitrile refining method Download PDF

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CN113501770B
CN113501770B CN202110928911.0A CN202110928911A CN113501770B CN 113501770 B CN113501770 B CN 113501770B CN 202110928911 A CN202110928911 A CN 202110928911A CN 113501770 B CN113501770 B CN 113501770B
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tower
acetonitrile
ammonia
acetone
outlet
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CN113501770A (en
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于博
耿尧辰
王志明
史文涛
庄大为
杨琦武
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China Tianchen Engineering Corp
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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C253/00—Preparation of carboxylic acid nitriles
    • C07C253/20—Preparation of carboxylic acid nitriles by dehydration of carboxylic acid amides
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
    • B01D3/009—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping in combination with chemical reactions
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C231/00—Preparation of carboxylic acid amides
    • C07C231/02—Preparation of carboxylic acid amides from carboxylic acids or from esters, anhydrides, or halides thereof by reaction with ammonia or amines
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C253/00—Preparation of carboxylic acid nitriles
    • C07C253/24—Preparation of carboxylic acid nitriles by ammoxidation of hydrocarbons or substituted hydrocarbons
    • C07C253/26—Preparation of carboxylic acid nitriles by ammoxidation of hydrocarbons or substituted hydrocarbons containing carbon-to-carbon multiple bonds, e.g. unsaturated aldehydes
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C253/00—Preparation of carboxylic acid nitriles
    • C07C253/32—Separation; Purification; Stabilisation; Use of additives
    • C07C253/34—Separation; Purification
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C45/00—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds
    • C07C45/78—Separation; Purification; Stabilisation; Use of additives
    • C07C45/786—Separation; Purification; Stabilisation; Use of additives by membrane separation process, e.g. pervaporation, perstraction, reverse osmosis
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C45/00—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds
    • C07C45/78—Separation; Purification; Stabilisation; Use of additives
    • C07C45/81—Separation; Purification; Stabilisation; Use of additives by change in the physical state, e.g. crystallisation
    • C07C45/82—Separation; Purification; Stabilisation; Use of additives by change in the physical state, e.g. crystallisation by distillation

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  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
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  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

Abstract

The invention provides an acetonitrile refining method, which is characterized in that unreacted ammonia gas discharged from an ammonification reactor is recovered through an ammonia recovery tower, the ammonia gas recovered by the ammonia recovery tower is introduced into an acrylonitrile device to obtain an acetonitrile crude product through an ammonification reaction of propylene, the acetonitrile crude product is decyanated through a decyanation tower, and the decyanated acetonitrile crude product is concentrated and rectified to obtain an acetonitrile finished product. According to the acetonitrile refining method, unreacted ammonia gas after acetic acid ammonification reaction is recovered through the ammonia recovery tower, and is used as a raw material of an acrylonitrile device, and a deep cooling reflux deamination technology is adopted, so that ammonia gas absorption by acid liquor is avoided to generate a large amount of ammonium salt wastewater.

Description

Acetonitrile refining method
Technical Field
The invention belongs to the technical field of chemical synthesis, and particularly relates to a method for refining acetonitrile.
Background
Acetonitrile is colorless liquid with pungent smell, and is an important fine chemical intermediate product and chemical solvent. Such as a solvent for extracting butadiene, a solvent for synthetic fibers and a solvent for certain special paints. Solvents used in the petroleum industry for removing tar, phenols, etc. from petroleum hydrocarbons. Solvents used in the oil industry for extracting fatty acids from animal and vegetable oils, and solvents used in pharmaceutical recrystallization of steroid drugs. Acetonitrile is an intermediate for synthesizing medicines and spices, and is a raw material for synthesizing a s-triazine nitrogenous fertilizer synergist. In addition, it can be used for synthesizing 2-methylpyridine, triazine, ethylamine, dipropionate, imidazole, propylene diacetonitrile, etc., and has many uses in the textile dyeing and lighting industries.
Acetonitrile can be synthesized by ammoxidation of olefins, or by direct ammonification of acetic acid. The most widely used industry is the byproduct acetonitrile of the propylene ammoxidation process, which is also the main source of acetonitrile in the market at present. However, acetonitrile production is limited by acrylonitrile production as a byproduct of acrylonitrile.
Disclosure of Invention
In view of the above, the present invention aims to provide a method for refining acetonitrile, which simplifies the process route, reduces the cost, reduces the energy consumption and improves the product yield.
In order to achieve the above purpose, the technical scheme of the invention is realized as follows:
the acetonitrile refining process is based on the design of co-production equipment of acrylonitrile and acetonitrile, and the crude acetonitrile product is produced through ammonia recovering, decyanating, concentrating and rectifying in the ammonifying reaction process and the refining process of the acrylonitrile equipment.
Wherein the acrylonitrile and acetonitrile co-production device comprises an ammonification reactor, an ammonia recovery tower, an acrylonitrile device, a decyanation tower, a purification reactor, an azeotropic tower, a concentration membrane component, an acetone tower and an acetonitrile tower,
the feed inlet of the ammonification reactor is communicated with an ammonia vaporizer and an acetic acid vaporizer, ammonia gas is injected into the ammonia vaporizer, acetic acid is injected into the acetic acid vaporizer, the molar ratio of ammonia gas to acetic acid is 1.01-1.99, the reaction temperature is 300-400 ℃, acetic acid ammonification reaction is carried out between the acetic acid and the ammonia gas in the ammonification reactor, and excessive unreacted ammonia gas is discharged through a gas phase outlet of the ammonification reactor;
the feed inlet of the ammonia recovery tower is communicated with the gas phase outlet of the ammonification reactor, the gas discharged from the ammonification reactor is injected into the ammonia recovery tower for recovery, the pressure at the top of the ammonia recovery tower is 150-600kPa, the temperature at the top of the ammonia recovery tower is-25-10 ℃, the ammonia recovery tower adopts a cryogenic reflux technology to recover unreacted ammonia discharged from the ammonification reactor, and the recovered ammonia is discharged through the gas phase outlet, compared with the prior art, the ammonia recovery tower can avoid using acid solution to absorb ammonia, reduce the discharge of wastewater containing ammonium salt, realize the recovery and utilization of ammonia and reduce the production waste;
the feed inlet of the acrylonitrile device is communicated with the gas phase outlet of the ammonia recovery tower, ammonia gas recovered by the ammonia recovery tower is used as a raw material, injected into the acrylonitrile device, and then subjected to propylene ammoxidation with propylene to finally obtain an acetonitrile crude product;
the feed inlet of the decyanation tower is communicated with the discharge outlet of the acrylonitrile device, the crude acetonitrile enters the decyanation tower for decyanation, the pressure at the top of the decyanation tower is 100-110kPa, the temperature at the top of the decyanation tower is 25-75 ℃, hydrocyanic acid and acrylonitrile in the crude acetonitrile are removed from the top of the decyanation tower, the wastewater is discharged from the bottom of the decyanation tower, and acetonitrile-water azeotrope is discharged from the gas phase in the middle of the decyanation tower;
the feed inlet of the purification reactor is communicated with a gas phase outlet at the middle part of the tower of the decyanation tower, and the gas discharged from the decyanation tower enters the purification reactor to remove residual hydrocyanic acid and acrylonitrile in acetonitrile-water azeotrope, wherein the temperature in the purification reactor is 25-55 ℃;
the feed inlet of the azeotropic tower is communicated with the tower bottom liquid outlet of the ammonia recovery tower and the discharge outlet of the purification reactor, the tower bottom liquid of the ammonia recovery tower and the outlet liquid of the purification reactor are mixed and then enter the azeotropic tower together, and acetonitrile-water vapor phase azeotrope containing acetone is extracted under the action of a tower top dephlegmator, wherein the tower top pressure of the azeotropic tower is 200-500kPa;
the feed inlet of the concentration membrane component is communicated with the gas phase outlet of the azeotropic tower, the concentration membrane component can concentrate acetonitrile-water vapor phase azeotrope containing acetone to obtain a concentrated acetonitrile-acetone crude product, a small amount of acetonitrile-containing wastewater separated from the vacuum side of the concentration membrane component returns to the azeotropic tower again for recycling, acetonitrile is finally discharged from the waste water in the tower kettle after being recovered, the water content of the outlet of the concentration membrane component is 1-15%, the pressure of the vacuum side of the membrane is 1-20kPa, the concentration membrane component adopts gas phase permeable membranes and is arranged in a serial or parallel connection mode, so that the membrane area required for realizing the same concentration effect can be reduced by 20-50%, and a large amount of equipment occupation and investment are saved;
the feed inlet of the acetone tower is communicated with the discharge outlet of the concentration membrane component, the concentrated acetonitrile-acetone crude product enters the acetone tower, finished acetone with purity of more than 99.5% is obtained at the top of the tower, and the pressure at the top of the acetone tower is 20-80kPa;
the feed inlet of the acetonitrile tower is communicated with the tower bottom liquid outlet of the acetone tower, the tower bottom liquid of the acetone tower enters the acetonitrile tower, the tower bottom of the acetonitrile tower obtains finished acetonitrile with the purity of more than 99.9 percent, the acetonitrile-water vapor phase azeotrope extracted by the tower top segregator returns to the concentration membrane component to be continuously concentrated, the tower top pressure of the acetone tower is 20-80kPa, and the tower top pressure of the acetonitrile tower is 200-500kPa.
The acetonitrile refining method based on the acrylonitrile and acetonitrile co-production device specifically comprises the following steps:
and step 1, enabling a gas-phase product at the outlet of the ammonification reactor to enter an ammonia recovery tower, recovering excessive ammonia by adopting a deep cooling reflux technology, and sending the ammonia to an acrylonitrile device for propylene ammoxidation.
Wherein the molar ratio of ammonia gas to acetic acid in the ammonification reactor is 1.01-1.99, and can be 1.01, 1.05, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9 and 1.99, and the reaction temperature is 300-400 ℃, and can be 300 ℃, 320 ℃, 340 ℃, 360 ℃, 380 ℃ and 400 ℃, for example. The overhead pressure of the ammonia recovery column is 150 to 600kPa, for example, 150kPa, 200kPa, 250kPa, 300kPa, 350kPa, 400kPa, 450kPa, 500kPa, 550kPa, 600kPa, and the overhead temperature is-25 to 10 ℃, for example, -25 ℃, -20 ℃, -15 ℃, -10 ℃, -5 ℃, 0 ℃, 5 ℃, 10 ℃.
Step 2, the crude acetonitrile product from the acrylonitrile device enters a decyanation tower, hydrocyanic acid and acrylonitrile are removed from the top of the tower, wastewater is discharged from the tower kettle, acetonitrile-water azeotrope is extracted from the gas phase in the middle of the tower, and the crude acetonitrile product enters a purification reactor to remove residual hydrocyanic acid and acrylonitrile.
Wherein the pressure at the top of the decyanation column is 100 to 110kPa, for example, 100kPa, 102kPa, 104kPa, 105kPa, 106kPa, 108kPa, 110kPa, the temperature at the top of the column is 25 to 75 ℃, for example, 25 ℃, 30 ℃, 35 ℃, 40 ℃, 45 ℃, 50 ℃, 55 ℃, 60 ℃, 65 ℃, 70 ℃, 75 ℃, and the reaction temperature of the purification reactor is 25 to 55 ℃, for example, 25 ℃, 30 ℃, 35 ℃, 40 ℃, 45 ℃, 50 ℃, 55 ℃.
Step 3, mixing tower bottom liquid of the ammonia recovery tower with outlet liquid of the purification reactor, then entering an azeotropic tower, extracting acetonitrile-water vapor phase azeotrope containing acetone by a column top dephlegmator, and sending the azeotrope to a concentration membrane component for concentration. And returning a small amount of acetonitrile-containing wastewater separated from the vacuum side of the concentration membrane component to the azeotropic tower, and discharging the wastewater from the tower kettle after the acetonitrile is recovered.
Wherein the top pressure of the azeotropic column is 200 to 500kPa, for example, 200kPa, 250kPa, 300kPa, 350kPa, 400kPa, 450kPa, 500kPa, the outlet water content of the concentrated film module is 1 to 15%, for example, 1%, 2%, 3%, 5%, 8%, 10%, 11%, 12%, 13%, 14%, 15%, and the film vacuum side pressure is 1 to 20kPa, for example, 1kPa, 4kPa, 8kPa, 10kPa, 12kPa, 14kPa, 16kPa, 18kPa, 20kPa. The concentration membrane component adopts gas phase permeation membranes, and is arranged in a serial or parallel mode.
And step 4, feeding the acetonitrile-acetone crude product concentrated by the concentration membrane component into an acetone tower, obtaining finished acetone with purity of more than 99.5% at the top of the acetone tower, and feeding tower bottom liquid into the acetonitrile tower. The finished acetonitrile with the purity of more than 99.9 percent is obtained at the tower bottom of the acetonitrile tower, and the acetonitrile-water vapor phase azeotrope extracted by the tower top segregator returns to the concentration membrane component to be continuously concentrated.
Wherein, the top pressure of the acetone tower is 20-80kPa, such as 20kPa, 30kPa, 40kPa, 50kPa, 60kPa, 70kPa, 80kPa, and the top pressure of the acetonitrile tower is 200-500kPa, such as 200kPa, 250kPa, 300kPa, 350kPa, 400kPa, 450kPa, 500kPa.
Compared with the prior art, the acetonitrile refining method has the following advantages:
(1) According to the acetonitrile refining method, unreacted ammonia gas after acetic acid ammonification reaction is recovered through the ammonia recovery tower, and is used as a raw material of an acrylonitrile device, and a deep cooling reflux deamination technology is adopted, so that ammonia gas is prevented from being absorbed by acid liquor to generate a large amount of ammonium salt wastewater;
(2) The concentrated membrane component in the acetonitrile refining method is fed as a gas phase product of an azeotropic tower, so that all materials are prevented from being vaporized through a membrane, the feed composition approaches to azeotropic composition, high energy consumption caused by excessive water vaporization is avoided, the water content of the feed is reduced, and the membrane separation efficiency is improved;
(3) The acetonitrile refining method controls the water content of the discharged material of the concentration membrane component to be 1-15%, the vacuum side pressure of the membrane to be 1-20kPa, the required membrane area can be reduced by 20-50%, and a large amount of equipment occupation and investment are saved;
(4) In the acetonitrile refining method, the materials in and out of the concentration membrane component are all in a gas phase, so that multiple evaporation and condensation of the materials are avoided, the energy utilization rate of the device is improved, and the heat load of rectification is reduced.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention. In the drawings:
fig. 1 is a schematic diagram of a connection structure of an acrylonitrile and acetonitrile co-production device according to an embodiment of the invention.
Reference numerals illustrate:
1. an ammonia vaporizer; 2. an acetic acid vaporizer; 3. an ammonification reactor; 4. an ammonia recovery tower; 5. an acrylonitrile unit; 6. a decyanation tower; 7. a purification reactor; 8. an azeotropic column; 9. concentrating the membrane component; 10. an acetone tower; 11. acetonitrile column.
Detailed Description
Unless defined otherwise, technical terms used in the following examples have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention pertains. The test reagents used in the following examples, unless otherwise specified, are all conventional biochemical reagents; the experimental methods are conventional methods unless otherwise specified.
The present invention will be described in detail with reference to the following examples and drawings.
In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, are merely for convenience in describing the present invention and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first", "a second", etc. may explicitly or implicitly include one or more such feature. In the description of the present invention, unless otherwise indicated, the meaning of "a plurality" is two or more.
In the description of the present invention, it should be noted that, unless explicitly specified and limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be either fixedly connected, detachably connected, or integrally connected, for example; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art in a specific case.
In the prior art, acetic acid ammonification method is to evaporate acetic acid and liquid ammonia, then take aluminum oxide as a catalyst, and obtain acetonitrile after dehydration reaction, wherein reaction products mainly comprise acetonitrile, water and acetone. The acetic acid conversion rate of the reaction is mainly determined by the feeding ratio of acetic acid to ammonia, and excessive ammonia is injected into the reactor generally, so that the acetic acid conversion rate can be effectively improved, the equipment corrosion can be greatly reduced, and the residual ammonia is recovered. Because the ammonia is used as raw material in both the ammoxidation of propylene and the ammoxidation of acetic acid, the excess ammonia in the ammoxidation of acetic acid can be recovered and injected as raw material into the acrylonitrile device for carrying out the ammoxidation of propylene, thereby realizing the co-production of acrylonitrile and acetonitrile by taking ammonia as medium and improving the productivity of acetonitrile products.
The acetonitrile refining method of the invention is based on an acrylonitrile and acetonitrile co-production device, wherein, as shown in figure 1, the acrylonitrile and acetonitrile co-production device comprises an ammonification reactor 3, an ammonia recovery tower 4, an acrylonitrile device 5, a decyanation tower 6, a purification reactor 7, an azeotropic tower 8, a concentration membrane component 9, an acetone tower 10 and an acetonitrile tower 11,
the feed inlet of the ammonification reactor 3 is communicated with the ammonia vaporizer 1 and the acetic acid vaporizer 2 through pipelines, ammonia is injected from the ammonia vaporizer 1, acetic acid is injected from the acetic acid vaporizer 2, the molar ratio of the ammonia to the acetic acid is 1.01-1.99, the reaction temperature is 300-400 ℃, acetic acid ammonification reaction is carried out between the acetic acid and the ammonia in the ammonification reactor 3, and excessive unreacted ammonia is discharged from a gas phase outlet of the ammonification reactor 3;
the feed inlet of the ammonia recovery tower 4 is communicated with the gas phase outlet of the ammonification reactor 3 through a pipeline, the gas discharged from the ammonification reactor 3 is injected into the ammonia recovery tower 4 for recovery, the pressure at the top of the ammonia recovery tower 4 is 150-600kPa, the temperature at the top of the ammonia recovery tower is-25-10 ℃, the ammonia recovery tower 4 adopts a deep cooling reflux technology to recover unreacted ammonia discharged from the ammonification reactor 3, and the recovered ammonia is discharged through the gas phase outlet, compared with the prior art, the ammonia recovery tower can avoid using acid solution to absorb the ammonia, reduce the discharge of ammonium salt-containing wastewater, realize the recovery and utilization of the ammonia and reduce the production waste;
the feed inlet of the acrylonitrile device 5 is communicated with the gas phase outlet of the ammonia recovery tower 4 through a pipeline, ammonia gas recovered by the ammonia recovery tower 4 is used as a raw material, injected into the acrylonitrile device 5, and then subjected to propylene ammoxidation with propylene to finally obtain an acetonitrile crude product;
the feed inlet of the decyanation tower 6 is communicated with the discharge outlet of the acrylonitrile device 5 through a pipeline, the crude acetonitrile enters the decyanation tower 6 for decyanation, the pressure at the top of the decyanation tower 6 is 100-110kPa, the temperature at the top of the tower is 25-75 ℃, hydrocyanic acid and acrylonitrile in the crude acetonitrile are removed at the top of the tower, waste water is discharged from the tower kettle, and acetonitrile-water azeotrope is discharged from the gas phase at the middle of the tower;
the feed inlet of the purification reactor 7 is communicated with a gas phase outlet in the middle of the tower of the decyanation tower 6 through a pipeline, and the gas discharged from the decyanation tower 6 enters the purification reactor 7 to remove residual hydrocyanic acid and acrylonitrile in acetonitrile-water azeotrope, wherein the temperature in the purification reactor 7 is 25-55 ℃;
the feed inlet of the azeotropic tower 8 is communicated with the tower bottom liquid outlet of the ammonia recovery tower 4 and the discharge outlet of the purification reactor 7 through pipelines, the tower bottom liquid of the ammonia recovery tower 4 and the outlet liquid of the purification reactor 7 are mixed and then enter the azeotropic tower 8 together, and acetonitrile-water vapor phase azeotrope containing acetone is extracted under the action of a tower top dephlegmator, wherein the tower top pressure of the azeotropic tower 8 is 200-500kPa;
the feed inlet of the concentration membrane component 9 is communicated with the gas phase outlet of the azeotropic tower 8 through a pipeline, the concentration membrane component 9 can concentrate acetonitrile-water vapor phase azeotrope containing acetone to obtain a concentrated acetonitrile-acetone crude product, a small amount of acetonitrile-containing wastewater separated from the vacuum side of the concentration membrane component 9 returns to the azeotropic tower 8 again for recycling, the wastewater is finally discharged from the tower kettle after the acetonitrile is recovered, the water content of the outlet of the concentration membrane component 9 is 1-15%, the side pressure of the membrane vacuum is 1-20kPa, and the concentration membrane component 9 adopts gas phase permeable membranes which are arranged in a serial or parallel connection mode, so that the membrane area required for realizing the same concentration effect can be reduced by 20-50%, thereby saving a large amount of equipment occupation and investment;
the feed inlet of the acetone tower 10 is communicated with the discharge outlet of the concentration membrane component 9 through a pipeline, the concentrated acetonitrile-acetone crude product enters the acetone tower 10, finished acetone with purity of more than 99.5% is obtained at the top of the tower, and the pressure at the top of the acetone tower 10 is 20-80kPa;
the feed inlet of the acetonitrile tower 11 is communicated with the tower bottom liquid outlet of the acetone tower 10 through a pipeline, the tower bottom liquid of the acetone tower 10 enters the acetonitrile tower 11, finished acetonitrile with the purity of more than 99.9% is obtained at the tower bottom of the acetonitrile tower 11, the acetonitrile-water vapor phase azeotrope extracted by the tower top segregator returns to the concentration membrane component 9 to be continuously concentrated, the tower top pressure of the acetone tower 10 is 20-80kPa, and the tower top pressure of the acetonitrile tower 11 is 200-500kPa.
The acetonitrile refining method based on the acrylonitrile and acetonitrile co-production device specifically comprises the following steps:
in step 1, the gas-phase product at the outlet of the ammonification reactor 3 enters an ammonia recovery tower 4, and excessive ammonia is recovered in the ammonia recovery tower 4 by adopting a deep cooling reflux technology and is sent to an acrylonitrile device 5 for propylene ammoxidation.
Step 2, the crude acetonitrile from the acrylonitrile device 5 enters a decyanation tower 6, hydrocyanic acid and acrylonitrile are removed at the top of the tower, wastewater is discharged from the bottom of the tower, acetonitrile-water azeotrope is extracted from the gas phase in the middle of the tower, and the acetonitrile-water azeotrope enters a purification reactor 7 to remove residual hydrocyanic acid and acrylonitrile.
Step 3, mixing tower bottom liquid of the ammonia recovery tower 4 with outlet liquid of the purification reactor 7, then entering an azeotropic tower 8, extracting acetonitrile-water vapor phase azeotrope containing acetone by a tower top dephlegmator, and sending the azeotrope to a concentration membrane component 9 for concentration. The wastewater containing a small amount of acetonitrile separated from the vacuum side of the concentration membrane component 9 is returned to the azeotropic tower 8, and the wastewater is discharged from the tower kettle after the acetonitrile is recovered.
And step 4, feeding the acetonitrile-acetone crude product concentrated by the concentration membrane component 9 into an acetone tower 10, obtaining finished acetone with purity of more than 99.5% at the top of the tower, and feeding tower bottom liquid into an acetonitrile tower 11. The finished acetonitrile with the purity of more than 99.9 percent is obtained at the tower bottom of the acetonitrile tower 11, and the acetonitrile-water vapor phase azeotrope extracted by the tower top dephlegmator returns to the concentration membrane component 9 to be concentrated continuously.
Example 1
Ammonia and acetic acid are added into an ammonification reactor 3 for ammonification reaction, the molar ratio of the ammonia to the acetic acid is 1.01, the reaction temperature is 350 ℃, the outlet gas phase product enters an ammonia recovery tower 4, the tower top pressure is 150kPa, the tower top temperature is-25 ℃, and the ammonia gas phase extracted from the tower top is sent to an acrylonitrile device 5.
The crude acetonitrile obtained by propylene ammoxidation is sent to a decyanation tower 6, the pressure at the top of the tower is 105kPa, and the temperature at the top of the tower is 25 ℃. The acetonitrile-water azeotrope is extracted from the gas phase in the middle of the tower and enters a purification reactor 7, and the temperature is controlled to be 25-55 ℃.
The outlet liquid of the purification reactor 7 is mixed with the tower bottom liquid of the ammonia recovery tower 4 and then enters an azeotropic tower 8, and the tower top pressure is 200kPa. The tower top dephlegmator extracts acetonitrile-water vapor phase azeotrope containing acetone, and sends the azeotrope to the concentration membrane component 9 for concentration.
The water content at the outlet of the concentration membrane module 9 was 1%, and the membrane vacuum side pressure was 1kPa. The crude acetonitrile-acetone product after being concentrated by the concentration membrane component 9 enters an acetone tower 10, the pressure at the top of the tower is 20kPa, the finished acetone with the purity of more than 99.5% is obtained at the top of the tower, and the tower bottom liquid is sent to an acetonitrile tower 11.
The pressure at the top of the acetonitrile tower 11 is 200kPa, and the finished acetonitrile with the purity of more than 99.9% is obtained at the tower bottom.
Example 2
Ammonia and acetic acid are added into an ammonification reactor 3 for ammonification reaction, the molar ratio of the ammonia to the acetic acid is 1.99, the reaction temperature is 350 ℃, the outlet gas phase product enters an ammonia recovery tower 4, the tower top pressure is 600kPa, the tower top temperature is 10 ℃, and the ammonia gas phase extracted from the tower top is sent to an acrylonitrile device 5.
The crude acetonitrile obtained by propylene ammoxidation is sent to a decyanation tower 6, the tower top pressure is 110kPa, and the tower top temperature is 75 ℃. The acetonitrile-water azeotrope is extracted from the gas phase in the middle of the tower and enters a purification reactor 7, and the temperature is controlled to be 25-55 ℃.
The outlet liquid of the purification reactor 7 is mixed with the tower bottom liquid of the ammonia recovery tower 4 and then enters the azeotropic tower 8, and the tower top pressure is 500kPa. The tower top dephlegmator extracts acetonitrile-water vapor phase azeotrope containing acetone, and sends the azeotrope to the concentration membrane component 9 for concentration.
The water content at the outlet of the concentration membrane module 9 was 15%, and the membrane vacuum side pressure was 20kPa. The crude acetonitrile-acetone product concentrated by the concentration membrane component 9 enters an acetone tower 10, the pressure at the top of the tower is 80kPa, the finished acetone product with the purity of more than 99.5% is obtained at the top of the tower, and the tower bottom liquid is sent to an acetonitrile tower 11.
The pressure at the top of the acetonitrile tower 11 is 500kPa, and the finished acetonitrile with the purity of more than 99.9% is obtained at the tower bottom.
The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, alternatives, and improvements that fall within the spirit and scope of the invention.

Claims (2)

1. The acetonitrile refining process includes the following steps:
step 1, enabling a gas-phase product at the outlet of an ammonification reactor to enter an ammonia recovery tower, recovering excessive ammonia gas in the ammonia recovery tower by adopting a deep cooling reflux technology, and sending the ammonia gas to an acrylonitrile device for propylene ammoxidation;
step 2, the crude acetonitrile from the acrylonitrile device enters a decyanation tower, hydrocyanic acid and acrylonitrile are removed at the top of the tower, wastewater is discharged from the tower bottom, acetonitrile-water azeotrope is extracted from the gas phase in the middle of the tower, and the crude acetonitrile enters a purification reactor to remove residual hydrocyanic acid and acrylonitrile;
step 3, mixing tower bottom liquid of the ammonia recovery tower with outlet liquid of the purification reactor, then entering an azeotropic tower, extracting acetonitrile-water vapor phase azeotrope containing acetone by a tower top dephlegmator, sending the azeotrope to a concentration membrane component for concentration, returning a small amount of acetonitrile-containing wastewater separated from the vacuum side of the concentration membrane component to the azeotropic tower, and discharging the wastewater from the tower bottom after acetonitrile is recovered;
step 4, the acetonitrile-acetone crude product concentrated by the concentrating membrane component enters an acetone tower, finished acetone with purity of more than 99.5 percent is obtained at the top of the acetone tower, tower bottom liquid is sent to the acetonitrile tower, finished acetonitrile with purity of more than 99.9 percent is obtained at the tower bottom of the acetonitrile tower, acetonitrile-water vapor phase azeotrope extracted by a tower top dephlegmator returns to the concentrating membrane component to be continuously concentrated,
the device applied to the acetonitrile refining method comprises an ammonification reactor;
the feed inlet of the ammonia recovery tower is communicated with the gas phase outlet of the ammonification reactor;
the feed inlet of the acrylonitrile device is communicated with a gas phase outlet of the ammonia recovery tower and also comprises a decyanation tower, and the feed inlet of the decyanation tower is communicated with a discharge outlet of the acrylonitrile device;
the feed inlet of the purification reactor is communicated with a gas phase outlet in the middle of the decyanation tower;
the feed inlet of the azeotropic tower is communicated with the tower bottom liquid outlet of the ammonia recovery tower and the discharge outlet of the purification reactor;
the feed inlet of the concentration membrane component is communicated with the gas phase outlet of the azeotropic tower;
the feed inlet of the acetone tower is communicated with the discharge outlet of the concentration membrane component;
an acetonitrile tower, a feed inlet of the acetonitrile tower is communicated with a tower bottom liquid outlet of the acetone tower,
the feeding mole ratio of ammonia gas and acetic acid in the ammonification reactor is 1.01-1.99, the reaction temperature is 300-400 ℃,
the pressure at the top of the ammonia recovery tower is 150-600kPa, the temperature at the top of the ammonia recovery tower is-25-10 ℃,
the pressure at the top of the decyanation tower is 100-110kPa, the temperature at the top of the decyanation tower is 25-75 ℃,
the reaction temperature of the purification reactor is 25-55 ℃, the top pressure of the azeotropic tower is 200-500kPa,
the pressure at the top of the acetone tower is 20-80kPa, the pressure at the top of the acetonitrile tower is 200-500kPa,
the water content of the discharged material of the concentration membrane component is 1-15%, and the vacuum side pressure of the membrane is 1-20kPa.
2. The method for purifying acetonitrile according to claim 1, wherein the concentration membrane component is arranged in series or in parallel by using a gas-phase permeation membrane, and the top outlet of the acetonitrile column is communicated with the feed inlet of the concentration membrane component.
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