CN109593059B - Method for separating pyridine-acetonitrile-water system by azeotropic-pressure swing distillation - Google Patents
Method for separating pyridine-acetonitrile-water system by azeotropic-pressure swing distillation Download PDFInfo
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- CN109593059B CN109593059B CN201811511877.1A CN201811511877A CN109593059B CN 109593059 B CN109593059 B CN 109593059B CN 201811511877 A CN201811511877 A CN 201811511877A CN 109593059 B CN109593059 B CN 109593059B
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07D—HETEROCYCLIC COMPOUNDS
- C07D213/00—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members
- C07D213/02—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members having three double bonds between ring members or between ring members and non-ring members
- C07D213/04—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members having three double bonds between ring members or between ring members and non-ring members having no bond between the ring nitrogen atom and a non-ring member or having only hydrogen or carbon atoms directly attached to the ring nitrogen atom
- C07D213/06—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members having three double bonds between ring members or between ring members and non-ring members having no bond between the ring nitrogen atom and a non-ring member or having only hydrogen or carbon atoms directly attached to the ring nitrogen atom containing only hydrogen and carbon atoms in addition to the ring nitrogen atom
- C07D213/16—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members having three double bonds between ring members or between ring members and non-ring members having no bond between the ring nitrogen atom and a non-ring member or having only hydrogen or carbon atoms directly attached to the ring nitrogen atom containing only hydrogen and carbon atoms in addition to the ring nitrogen atom containing only one pyridine ring
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- 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
Abstract
The invention relates to a method for separating a pyridine-acetonitrile-water system by azeotropic-pressure swing distillation. The device of the method comprises an azeotropic tower, a high-pressure tower and a low-pressure tower, acetonitrile which is a substance contained in the azeotropic tower is used as an entrainer in the azeotropic distillation process, the acetonitrile and water are separated from a ternary system through azeotropic distillation to obtain a pyridine product with qualified purity, and then the acetonitrile and water system is further separated through pressure swing distillation, so that the efficient separation of the pyridine, the acetonitrile and the water is realized by adopting a process combining the azeotropic distillation and the pressure swing distillation. The invention does not introduce other components, ensures the purity of the product, and can recycle the entrainer.
Description
Technical Field
The invention belongs to the field of chemical separation and purification, and particularly relates to a method for separating a pyridine-acetonitrile-water system by azeotropic-pressure swing distillation.
Background
Pyridine and acetonitrile are important chemical and medical raw materials, and form pyridine-acetonitrile-water mixed waste liquid in the process of synthesizing the medicine for treating hepatitis C. Pyridine has a boiling point of 115.3 ℃ at normal pressure, forms a minimum azeotrope with water, and has an azeotropic composition of 57w percent of water and an azeotropic temperature of 94 ℃. The normal pressure boiling point of acetonitrile is 81.6 ℃, the acetonitrile and water form the lowest azeotrope, the azeotropic composition is 15w percent of water, and the azeotropic temperature is 76 ℃. The pyridine, the acetonitrile and the water do not form ternary azeotropy, but the pyridine, the water, the acetonitrile and the water respectively form minimum azeotropy, so the system can not be separated by common rectification, and the system with azeotropy is generally separated by pressure swing rectification, extractive rectification or azeotropic rectification. The single use of a rectification method to separate the ternary system is not enough to obtain a high-purity product, and an extractant is required to be used in the extraction and rectification, other substances are introduced, and the product purity is influenced, so that the extraction and rectification are not suitable to be selected.
Disclosure of Invention
The invention aims to provide a method for separating a pyridine-acetonitrile-water system by azeotropic-pressure swing distillation, which realizes the recycling of pyridine and acetonitrile. The main apparatus of the present invention comprises an azeotropic column, a high pressure column and a low pressure column. In the azeotropic distillation process, acetonitrile which is a substance contained in the azeotropic distillation process is used as an entrainer, other components are not introduced, the product purity is ensured, and the entrainer can be recycled.
The technical scheme of the invention is as follows:
a method for separating a pyridine-acetonitrile-water system by azeotropic-pressure swing distillation comprises the following steps:
(1) feeding pyridine-acetonitrile-water feed liquid into an azeotropic tower, simultaneously feeding an entrainer acetonitrile into the azeotropic tower, and carrying out azeotropic rectification to obtain a product pyridine in a tower kettle; condensing the tower top steam by a condenser, refluxing part of the tower top steam to the azeotropic tower, and sending the rest of the tower top steam to the high-pressure tower by a pressure pump;
wherein the mass ratio is entrainer: 3.3-4.6: 1; the theoretical plate number of the azeotropic tower is 13-20 plates, the tower top temperature is 75-77 ℃, the tower bottom temperature is 113-116 ℃, the reflux ratio is 1.0-3.4, and the operating pressure is 101.325 kPa;
(2) the product acetonitrile is obtained from the tower kettle of the high-pressure tower, and part of the acetonitrile is used as an entrainer of the azeotropic tower to circularly enter the azeotropic tower; condensing the tower top steam by a condenser, refluxing part of the tower top steam to the high-pressure tower, and feeding the rest of the tower top steam to the low-pressure tower;
wherein, the theoretical plate number of the high-pressure tower is 14-22 plates, the tower top temperature is 131-134 ℃, the tower bottom temperature is 136-146 ℃, the reflux ratio is 0.4-1.6, and the operation pressure is 450-600 kPa;
(3) obtaining pure water at the tower kettle of the low-pressure tower, condensing the steam at the tower top by a condenser to obtain acetonitrile-water azeotrope, partially refluxing the acetonitrile-water azeotrope to the low-pressure tower, and feeding the rest into the high-pressure tower for cyclic treatment;
wherein the theoretical plate number of the low-pressure tower is 7-15 plates, the tower top temperature is 50-53 ℃, the tower bottom temperature is 74-77 ℃, the operation pressure is 40-100kPa, and the reflux ratio is 1-3.
The feed liquid comprises, by mass, 14-25% of pyridine, 26-37% of acetonitrile and 43-55% of water.
The purity of the obtained acetonitrile and pyridine products is more than 99.5 percent.
The feeding position of the azeotropic tower is 7-13 plates; the feeding position of the high-pressure tower is 5-13 plates; the feed position to the lower pressure column is 5 to 11 plates.
The feeding position of the entrainer of the azeotropic tower is 5-11 plates.
The invention has the substantive characteristics that:
the material of the invention is pyridine-acetonitrile-water which does not form ternary azeotrope, but pyridine-water and acetonitrile-water respectively form lowest azeotrope, and acetonitrile-water system is sensitive to pressure. As the pyridine and the water are more difficult to separate than the acetonitrile and the water, the first step of the invention is to separate the acetonitrile and the water from a ternary system by azeotropic distillation to obtain a pyridine product with qualified purity, and then further separate the acetonitrile and the water system by pressure swing distillation, thereby realizing the high-efficiency separation of the pyridine, the acetonitrile and the water by adopting a process combining the azeotropic distillation and the pressure swing distillation.
The invention has the following beneficial effects:
(1) the method realizes the high-efficiency separation of pyridine, acetonitrile and water, the product purity of the pyridine and the acetonitrile is up to more than 99.5 percent, the pyridine and the acetonitrile can be directly recycled, the investment cost of raw materials is reduced, and the problem of difficult azeotropic separation of pyridine-water and acetonitrile-water is solved.
(2) The invention uses the substance acetonitrile contained in the system as the entrainer, does not introduce other components, ensures the product quality, reduces the separation difficulty, and reduces the equipment investment cost and energy consumption.
(3) The invention realizes the recycling of pyridine and acetonitrile, avoids the discharge of industrial waste liquid to the environment, reduces pollution and protects the environment.
(4) The invention has the advantages of simple process, convenient operation, low cost, low energy consumption and the like.
Drawings
FIG. 1 is a schematic flow chart of the present invention.
In the figure: t1-azeotropic distillation column; t2-high pressure column; T3-Low pressure column; a P-booster pump; the numbers indicate the respective streams.
The present invention is described in further detail below. The following examples are merely illustrative of the present invention and do not represent or limit the scope of the claims, which are defined by the claims.
Detailed Description
The technical scheme of the invention is further explained by the specific implementation mode in combination with the attached drawings.
Example 1:
(1) the feed flow rate was 5kg/hr, the mass composition was 19.8% pyridine, 31.83% acetonitrile, 48.37% water, and the amount of azeotropic agent acetonitrile was 19.5 kg/hr. The number of trays of an azeotropic tower T1 was 15, the reflux ratio was 2.2, the operating pressure was 101.325kPa, the feed position of the raw material was the 9 th tray, the feed position of the entrainer was the 7 th tray, 99.97% of pyridine was obtained in the bottom of the tower, the yield was 0.95kg/hr, and the temperature in the bottom of the tower was 115.1 ℃. An acetonitrile-water mixture is obtained at the top of the tower, the mass composition of the acetonitrile-water mixture is 89.6 percent, the water content is 10.4 percent, part of the acetonitrile-water mixture flows back to the azeotropic tower, and the rest of the acetonitrile-water mixture is sent to a high-pressure tower T2 through a pressure pump, and the temperature at the top of the tower is 76.6 ℃.
(2) The number of trays in the high-pressure tower T2 is 18, the reflux ratio is 1, the operation pressure is 530kPa, the feeding position is the 9 th tray, 99.61 percent of acetonitrile is obtained in the tower kettle, the yield is 22.6kg/hr, part of the acetonitrile is used as an entrainer to circulate into an azeotropic tower T1, and the temperature in the tower kettle is 144.6 ℃. The top of the column obtained another acetonitrile-water mixture under azeotropic composition, the mass composition of acetonitrile 75.1%, water 24.9%, partly returned to the high pressure column, the rest sent to the low pressure column T3, the temperature of the top of the column was 133.2 ℃.
(3) The low-pressure column T3 had a plate number of 11, a reflux ratio of 2, an operating pressure of 40kPa, a feed position of the 7 th plate, a column bottom at which 99.99% of water was obtained at a flow rate of 0.95kg/hr and a column bottom temperature of 75.8 ℃. Acetonitrile-water azeotrope is obtained at the tower top, the mass composition of the acetonitrile-water azeotrope is 83.9 percent, the water content is 16.1 percent, part of the acetonitrile-water azeotrope flows back to the low-pressure tower, the rest of the acetonitrile-water azeotrope enters the high-pressure tower T2 for cyclic treatment, and the tower top temperature is 51.4 ℃.
Example 2:
(1) the feeding flow rate is 6kg/hr, the mass composition is pyridine 21%, acetonitrile 33%, water 46%, and the dosage of entrainer acetonitrile is 20 kg/hr. The number of trays of an azeotropic tower T1 was 17, the reflux ratio was 2, the operating pressure was 101.325kPa, the feed position of the raw material was the 11 th plate, the feed position of the entrainer was the 9 th plate, 99.86% of pyridine was obtained in the bottom of the tower, the yield was 1kg/hr, and the temperature of the bottom of the tower was 115.3 ℃. An acetonitrile-water mixture is obtained at the top of the tower, the mass composition of the acetonitrile is 87.9 percent, the water is 12.1 percent, part of the acetonitrile flows back to the azeotropic tower, the rest is sent to a high-pressure tower T2 by a pressure pump, and the temperature at the top of the tower is 76.7 ℃.
(2) The number of trays in the high-pressure tower T2 is 20, the reflux ratio is 0.5, the operation pressure is 550kPa, the feeding position is the 11 th tray, 99.63 percent of acetonitrile is obtained in the tower kettle, the yield is 23.8kg/hr, part of the acetonitrile is used as an entrainer to circulate into an azeotropic tower T1, and the temperature of the tower kettle is 136.6 ℃. The top of the column obtained another acetonitrile-water mixture under azeotropic composition, the mass composition of which was acetonitrile 76.6%, water 23.4%, a portion of which refluxed to the high pressure column, the remainder was sent to the low pressure column T3, the temperature at the top of the column was 133.5 ℃.
(3) The low-pressure column T3 had a tray number of 14, a reflux ratio of 1.2, an operating pressure of 50kPa, a feed position of the 8 th tray, a column bottom at which 99.95% of water was obtained at a flow rate of 1.2kg/hr and a column bottom temperature of 75.9 ℃. Acetonitrile-water azeotrope is obtained at the tower top, the mass composition of acetonitrile is 84.5 percent, water is 15.5 percent, part of acetonitrile flows back to the low-pressure tower, the rest acetonitrile enters the high-pressure tower T2 for circular treatment, and the tower top temperature is 51.1 ℃.
The azeotropic distillation tower, the high-pressure tower and the low-pressure tower are all plate towers or packed towers.
The applicant states that the process of the present invention is illustrated by the above examples, but the present invention is not limited to the above procedures, i.e. it does not mean that the present invention must rely on the above procedures to be carried out. It will be apparent to those skilled in the art that any modification of the present invention, equivalent substitutions of selected materials and additions of auxiliary components, selection of specific modes and the like, which are within the scope and disclosure of the present invention, are contemplated by the present invention.
The preferred embodiments of the present invention have been described in detail, however, the present invention is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solution of the present invention within the technical idea of the present invention, and these simple modifications are within the protective scope of the present invention.
It should be noted that the various technical features described in the above embodiments can be combined in any suitable manner without contradiction, and the invention is not described in any way for the possible combinations in order to avoid unnecessary repetition.
In addition, any combination of the various embodiments of the present invention is also possible, and the same should be considered as the disclosure of the present invention as long as it does not depart from the spirit of the present invention.
The invention is not the best known technology.
Claims (5)
1. A method for separating a pyridine-acetonitrile-water system by azeotropic-pressure swing distillation is characterized by comprising the following steps:
(1) feeding pyridine-acetonitrile-water feed liquid into an azeotropic tower, simultaneously feeding an entrainer acetonitrile into the azeotropic tower, and carrying out azeotropic rectification to obtain a product pyridine in a tower kettle; condensing the tower top steam by a condenser, refluxing part of the tower top steam to the azeotropic tower, and sending the rest of the tower top steam to the high-pressure tower by a pressure pump;
wherein the mass ratio is entrainer: raw material liquid = 3.3-4.6: 1; the number of plates of the azeotropic tower is 13-20, the temperature at the top of the tower is 75-77 ℃, the temperature at the bottom of the tower is 113-116 ℃, the reflux ratio is 1.0-3.4, and the operating pressure is 101.325 kPa;
(2) the product acetonitrile is obtained from the tower kettle of the high-pressure tower, and part of the acetonitrile is used as an entrainer of the azeotropic tower to circularly enter the azeotropic tower; condensing the tower top steam by a condenser, refluxing part of the tower top steam to the high-pressure tower, and feeding the rest of the tower top steam to the low-pressure tower;
wherein the plate number of the high-pressure tower is 14-22 plates, the tower top temperature is 131-134 ℃, the tower bottom temperature is 136-146 ℃, the reflux ratio is 0.4-1.6, and the operating pressure is 450-600 kPa;
(3) pure water is obtained from the tower kettle of the low-pressure tower, the steam at the tower top is condensed by a condenser to obtain acetonitrile-water azeotrope, part of the acetonitrile-water azeotrope flows back to the low-pressure tower, and the rest enters the high-pressure tower for cyclic treatment;
wherein the plate number of the low-pressure tower is 7-15, the tower top temperature is 50-53 ℃, the tower bottom temperature is 74-77 ℃, the operation pressure is 40-100kPa, and the reflux ratio is 1-3.
2. The method for separating a pyridine-acetonitrile-water system according to claim 1, wherein the feed liquid comprises, by mass, 14-25% of pyridine, 26-37% of acetonitrile, and 43-55% of water.
3. The process of claim 1 wherein said product purity of acetonitrile and pyridine is greater than 99.5%.
4. The process for the separation of a pyridine-acetonitrile-water system according to claim 1, wherein the feed position of the azeotropic column is 7 to 13 plates; the feeding position of the high-pressure tower is 5-13 plates; the feed position to the lower pressure column is 5 to 11 plates.
5. The process for separating pyridine-acetonitrile-water system according to claim 1, wherein the azeotropic column has an entrainer feed position of 5 to 11 plates.
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| CN113979925B (en) * | 2021-09-30 | 2023-05-19 | 索闻特环保科技(上海)有限公司 | Method for extracting 3-methylpyridine from pesticide production waste liquid |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| RU2599132C1 (en) * | 2015-06-30 | 2016-10-10 | Федеральное государственное бюджетное образовательное учреждение высшего образования "Московский технологический университет" | Method of separating mixture of solvents methanol-tetrahydrofuran-acetonitrile-water-pyridine |
| CN108373427A (en) * | 2018-03-13 | 2018-08-07 | 索闻特环保科技(上海)有限公司 | The separation method of the waste liquid of picoline containing 3- and acetonitrile |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| RU2599132C1 (en) * | 2015-06-30 | 2016-10-10 | Федеральное государственное бюджетное образовательное учреждение высшего образования "Московский технологический университет" | Method of separating mixture of solvents methanol-tetrahydrofuran-acetonitrile-water-pyridine |
| CN108373427A (en) * | 2018-03-13 | 2018-08-07 | 索闻特环保科技(上海)有限公司 | The separation method of the waste liquid of picoline containing 3- and acetonitrile |
Non-Patent Citations (2)
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| 变压精馏和萃取精馏分离乙腈和水工艺模拟及优化;余美琼等;《中南大学学报自然科学版》;20140930;第45卷(第9期);全文 * |
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