CN110590603A - Method for continuously rectifying and purifying m-phthalonitrile - Google Patents
Method for continuously rectifying and purifying m-phthalonitrile Download PDFInfo
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- CN110590603A CN110590603A CN201910990191.3A CN201910990191A CN110590603A CN 110590603 A CN110590603 A CN 110590603A CN 201910990191 A CN201910990191 A CN 201910990191A CN 110590603 A CN110590603 A CN 110590603A
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Abstract
The invention provides a method for continuously rectifying and purifying isophthalonitrile, which realizes the continuous and stable purification of isophthalonitrile through the steps of melting, continuous evaporation and vaporization and rectification purification, obtains a product with the purity of isophthalonitrile being more than or equal to 99.82 wt%, and reduces the content of cyanobenzamide in the product, thereby reducing the content of hexachlorobenzene in downstream chlorothalonil products, relieving the environmental pressure, realizing continuous and stable production and low operation cost.
Description
Technical Field
The invention relates to the field of pesticide refining, in particular to a method for continuously rectifying and purifying isophthalonitrile.
Background
Isophthalonitrile (IPN) is an important organic raw material for organic synthesis, and is used for preparing plastics, synthetic fibers, pesticides (chlorothalonil), epoxy resin curing agents and the like. Tetrachloroisophthalonitrile synthesized by chlorination of isophthalonitrile is a high-efficiency and low-toxicity bactericide; the m-xylylenediamine prepared by hydrogenation of m-phthalonitrile is an epoxy resin curing agent with excellent performance, and is also a raw material of polyurethane and nylon resin.
At present, the main method for synthesizing isophthalonitrile is an ammoxidation method, namely, m-xylene, ammonia gas and oxygen are subjected to ammoxidation reaction under the action of a catalyst to prepare isophthalonitrile. However, the isophthalonitrile produced by the ammoxidation method has low purity and high amide content, and is crude isophthalonitrile. The crude isophthalonitrile can provide raw materials for subsequent organic synthesis after purification and refining, the main trapping modes of the isophthalonitrile at present are thin-wall trapping and water spraying trapping, but the isophthalonitrile products obtained by the two trapping methods still have high amide content, the high amide content can cause more residues in a melter in the production process of downstream chlorothalonil, and the impurity hexachlorobenzene in the chlorothalonil products can also have high content and great harm to the environment.
CN201384868Y discloses a water spraying and collecting mode, which adopts a spraying tower, a secondary absorption tower, a filter press and a drying tower device to collect and recycle materials in a water mist mode, thereby reducing the investment cost of the device to a certain extent. However, the method adopts a filter press to separate the solid-liquid mixture, the filter press is intermittent equipment and cannot be continuously operated with subsequent drying equipment, and ammonia gas escapes from the filter press in the operation process to greatly influence the labor environment of workers.
CN106892839B discloses a method for refining isophthalonitrile, which comprises the steps of introducing a crude isophthalonitrile raw material into a distillation kettle, cooling steam of the distilled isophthalonitrile through a heat exchanger, introducing into a receiving kettle for heat preservation, and finally slicing through a slicer to obtain a refined isophthalonitrile finished product. The method improves the purity of the intermediate phthalonitrile product, but the method adopts the intermittent distillation process to refine the isophthalonitrile, the refined isophthalonitrile product content is only 99.5 percent, and the intermittent process not only easily causes the instability of the product quality, but also is difficult to realize continuous production, and increases the production cost.
CN1202072C discloses a solvent refining method for purifying isophthalonitrile, which improves the quality and recovery rate of products. However, the method adopts two-stage rectifying towers, so that the energy consumption is high, the isophthalonitrile has thermal instability, and the modification or deterioration can occur in the primary de-heavy rectification process due to the long rectification time, so that the reactions such as amidation, polymerization and the like are caused, and the yield and the quality of the product are reduced.
In summary, the existing refining or trapping method has the problems of high amide content in the isophthalonitrile product, unstable product quality, low yield, difficulty in continuous production and the like, and the high amide content can cause more residues in a melter in the production process of downstream chlorothalonil, and can also cause high content of impurity hexachlorobenzene in the chlorothalonil product, so that the pollution to the environment is great.
Therefore, it is required to develop a continuous production method of isophthalonitrile with high yield, high purity and low content of m-cyanobenzamide, thereby reducing the content of hexachlorobenzene in the subsequent chlorothalonil product, reducing the amount of residues in a melter in a chlorothalonil production device and reducing the production cost.
Disclosure of Invention
In view of the problems in the prior art, the invention provides a method for continuously rectifying and purifying isophthalonitrile, wherein an isophthalonitrile raw material is subjected to rectification and purification after being melted and continuously evaporated and vaporized, so that the problems of unstable quality and low purity of an isophthalonitrile product are solved, the continuous production of high-purity isophthalonitrile is realized, the production cost and the amide content in the product are reduced, the content of hexachlorobenzene in a downstream chlorothalonil product is obviously reduced, the product quality of chlorothalonil is improved, and the environmental pressure is relieved.
In order to achieve the purpose, the invention adopts the following technical scheme:
the invention provides a method for continuously rectifying and purifying isophthalonitrile, which comprises the following steps:
(1) melting an isophthalonitrile raw material, and continuously evaporating and vaporizing the melted isophthalonitrile;
(2) and rectifying the continuously evaporated and vaporized isophthalonitrile to obtain purified isophthalonitrile.
The method provided by the invention melts the isophthalonitrile raw material and then evaporates and vaporizes, wherein the melting process not only ensures the liquid-phase feeding of the isophthalonitrile raw material in the evaporating and vaporizing process, but also can play a buffering role, thereby realizing the continuous and stable feeding of the isophthalonitrile raw material; meanwhile, the m-phthalonitrile is evaporated and vaporized and then rectified and purified, so that continuous production can be realized, the product quality is stable, the purity and the yield are high, and the content of cyanobenzamide in the product is remarkably reduced, so that the residue generation amount of a melting kettle in a downstream chlorothalonil production device is relieved, and the product quality of the downstream chlorothalonil is improved.
The intermediate phthalonitrile raw material provided by the invention is a liquid crude isophthalonitrile raw material from a batch distillation process receiving kettle, the crude isophthalonitrile raw material is liquid isophthalonitrile from which mechanical impurities and insoluble substances are removed after simple distillation, and the method has low pretreatment requirement on the isophthalonitrile raw material and high universality.
Preferably, in the step (1), the melting process is heated by using heat transfer oil.
Preferably, the temperature of the heat conducting oil in the melting process is 160 to 250 ℃, for example, 160 ℃, 165 ℃, 170 ℃, 175 ℃, 180 ℃, 185 ℃, 190 ℃, 195 ℃, 200 ℃, 205 ℃, 210 ℃, 215 ℃, 220 ℃, 225 ℃, 230 ℃, 235 ℃, 240 ℃, 245 ℃ or 250 ℃, preferably 180 to 200 ℃.
Preferably, the continuous evaporation and vaporization process in the step (1) adopts heat conduction oil for heating.
Preferably, the temperature of the heat conducting oil in the continuous evaporation and vaporization process is 230 to 300 ℃, for example, 230 ℃, 235 ℃, 240 ℃, 245 ℃, 250 ℃, 255 ℃, 260 ℃, 265 ℃, 270 ℃, 275 ℃, 280 ℃, 285 ℃, 290 ℃, 295 ℃ or 300 ℃, preferably 260 to 280 ℃.
Preferably, the vacuum degree of the continuous evaporation and vaporization process is 0.07-0.098 MPa, such as 0.07MPa, 0.075MPa, 0.078MPa, 0.080MPa, 0.082MPa, 0.085MPa, 0.088MPa, 0.090MPa, 0.092MPa, 0.095MPa or 0.098MPa, preferably 0.09-0.095 MPa.
Preferably, the liquid phase isophthalonitrile that has not completely vaporized during the continuous vaporization is collected.
The method provided by the invention collects liquid-phase isophthalonitrile which is not completely vaporized in the continuous evaporation and vaporization process through the kettle, further ensures the continuous stability of the isophthalonitrile raw material vaporization, reduces the coking phenomenon at the bottom of the evaporator, prevents the evaporator from being damaged, and further ensures the stability of the feeding components in the rectification process.
The method provided by the invention has the advantages that the liquid-phase isophthalonitrile which is collected in the kettle and is not completely vaporized in the continuous evaporation and vaporization process is recycled to the upstream batch process distillation kettle, so that the utilization rate of resources is improved, and the production cost is reduced.
Preferably, the collection process is heated by using heat transfer oil.
Preferably, the temperature of the heat conducting oil in the collecting process is 160-250 ℃, for example 160 ℃, 165 ℃, 170 ℃, 175 ℃, 180 ℃, 185 ℃, 190 ℃, 195 ℃, 200 ℃, 205 ℃, 210 ℃, 215 ℃, 220 ℃, 225 ℃, 230 ℃, 235 ℃, 240 ℃, 245 ℃ or 250 ℃, preferably 180-200 ℃.
Preferably, the rectification process in step (2) is heated by using heat transfer oil.
Preferably, the rectification temperature in the rectification process is 160-200 ℃, for example, 160 ℃, 165 ℃, 170 ℃, 175 ℃, 180 ℃, 185 ℃, 190 ℃, 195 ℃ or 200 ℃, preferably 160-180 ℃.
Preferably, the stripping temperature in the rectification process is 230 to 300 ℃, for example, 230 ℃, 235 ℃, 240 ℃, 245 ℃, 250 ℃, 255 ℃, 260 ℃, 265 ℃, 270 ℃, 275 ℃, 280 ℃, 285 ℃, 290 ℃, 295 ℃ or 300 ℃, preferably 260 to 280 ℃.
Preferably, the condensation temperature at the top of the rectification column is 160-200 ℃, for example 160 ℃, 165 ℃, 170 ℃, 175 ℃, 180 ℃, 185 ℃, 190 ℃, 195 ℃ or 200 ℃, preferably 160-180 ℃.
Preferably, the reboiling temperature of the bottom of the rectification process is 230 to 300 ℃, for example, 230 ℃, 235 ℃, 240 ℃, 245 ℃, 250 ℃, 255 ℃, 260 ℃, 265 ℃, 270 ℃, 275 ℃, 280 ℃, 285 ℃, 290 ℃, 295 ℃ or 300 ℃, preferably 260 to 280 ℃.
Preferably, the degree of vacuum in the rectification process is 0.07 to 0.098MPa, for example, 0.07MPa, 0.075MPa, 0.078MPa, 0.080MPa, 0.082MPa, 0.085MPa, 0.088MPa, 0.090MPa, 0.092MPa, 0.095MPa or 0.098MPa, preferably 0.09 to 0.095 MPa.
Preferably, the non-condensable gas in the rectification process in the step (2) is subjected to secondary condensation, and a liquid-phase isophthalonitrile product subjected to secondary condensation is recovered.
The method provided by the invention further recovers the isophthalonitrile in the non-condensable gas by carrying out secondary condensation on the non-condensable gas in the rectification process, thereby further improving the recovery rate of the isophthalonitrile and improving the resource utilization rate.
Preferably, the secondary condensation process adopts heat transfer oil for heat exchange.
Preferably, the temperature of the heat conducting oil in the secondary condensation process is 160-200 ℃, for example, 160 ℃, 165 ℃, 170 ℃, 175 ℃, 180 ℃, 185 ℃, 190 ℃, 195 ℃ or 200 ℃, preferably 160-180 ℃.
Preferably, the high-boiling residues of the rectification process are periodically discharged and barreled in the step (2).
Preferably, the high boilers are m-cyanobenzamides and/or phthalimides.
According to the method provided by the invention, high-boiling-point substances in the rectification process, such as m-cyanobenzamide and phthalimide, are subjected to slag discharge and barreling and are periodically treated as solid wastes, so that the continuous and stable operation of the rectification and purification process is further ensured, the stability of the quality of m-phthalonitrile products is further improved, the content of the intermediate cyanobenzamide in the products is reduced, and the product quality of downstream chlorothalonil is improved.
Preferably, the slag discharging process adopts heat conducting oil for heating.
Preferably, the temperature of the heat conducting oil in the deslagging process is 230-300 ℃, for example, 230 ℃, 235 ℃, 240 ℃, 245 ℃, 250 ℃, 255 ℃, 260 ℃, 265 ℃, 270 ℃, 275 ℃, 280 ℃, 285 ℃, 290 ℃, 295 ℃ or 300 ℃, preferably 260-280 ℃.
Preferably, after the step (2), the method further comprises the step (3): and (3) receiving the isophthalonitrile product purified in the step (2).
Preferably, the isophthalonitrile product purified by the rectification in step (2) and/or secondarily condensed is received.
Preferably, the receiving process adopts heat conducting oil for heating.
Preferably, the temperature of the heat conducting oil in the receiving process is 160-200 ℃, for example, 160 ℃, 165 ℃, 170 ℃, 175 ℃, 180 ℃, 185 ℃, 190 ℃, 195 ℃ or 200 ℃, preferably 160-180 ℃.
Preferably, the vacuum degree of the receiving process is 0.07-0.098 MPa, such as 0.07MPa, 0.075MPa, 0.078MPa, 0.080MPa, 0.082MPa, 0.085MPa, 0.088MPa, 0.090MPa, 0.092MPa, 0.095MPa or 0.098MPa, preferably 0.09-0.095 MPa.
Preferably, the isophthalonitrile product received in step (3) is sliced or passed to a chlorothalonil plant.
Preferably, the gas phase which is not completely condensed in the receiving process of the step (3) is subjected to secondary condensation, and a secondary condensed liquid-phase phthalonitrile product is recovered.
Preferably, the gas-phase isophthalonitrile which is not completely condensed in the recondensation in the step (3) is collected to obtain a powder isophthalonitrile product.
Preferably, the capture process employs water or cold air for condensation.
Preferably, the temperature of the trapping process is 40 to 100 ℃, for example, 40 ℃, 45 ℃, 50 ℃, 55 ℃, 60 ℃, 65 ℃, 70 ℃, 75 ℃, 80 ℃, 85 ℃, 90 ℃, 95 ℃ or 100 ℃, preferably 50 to 70 ℃.
Preferably, the vacuum degree in the capturing process is 0.07 to 0.098MPa, and may be, for example, 0.07MPa, 0.075MPa, 0.078MPa, 0.080MPa, 0.082MPa, 0.085MPa, 0.088MPa, 0.090MPa, 0.092MPa, 0.095MPa, or 0.098MPa, and preferably 0.09 to 0.095 MPa.
As a preferred technical scheme of the invention, the method comprises the following steps:
(1) melting an isophthalonitrile raw material at 160-250 ℃, continuously evaporating and vaporizing the melted isophthalonitrile at 230-300 ℃ and 0.07-0.098 MPa, and collecting liquid-phase isophthalonitrile which is not completely vaporized at 160-250 ℃;
(2) rectifying the continuously evaporated and vaporized isophthalonitrile under the pressure of 0.07-0.098 MPa to obtain purified isophthalonitrile, wherein the rectification temperature in the rectification process is 160-200 ℃, the stripping temperature is 230-300 ℃, the condensation temperature at the top of the tower is 160-200 ℃, and the reboiling temperature at the bottom of the tower is 230-300 ℃; carrying out secondary condensation on the non-condensable gas in the rectification process at the temperature of 160-200 ℃, recovering a liquid-phase isophthalonitrile product subjected to secondary condensation, and periodically discharging and barreling high-boiling-point substances in the rectification process at the temperature of 230-300 ℃;
(3) and (3) receiving the m-phthalonitrile product purified and secondarily condensed in the rectification process in the step (2) under the conditions of 160-200 ℃ and 0.07-0.098 MPa, re-condensing the gas phase which is not completely condensed in the receiving process, and recovering the re-condensed liquid-phase phthalonitrile product.
Compared with the prior art, the invention has at least the following beneficial effects:
(1) the method for continuously rectifying and purifying the isophthalonitrile provided by the invention can improve the content of the isophthalonitrile in the product and keep the purity of the isophthalonitrile stable to be more than or equal to 99.82 wt% and the molar yield to be more than or equal to 95.6% by melting the isophthalonitrile and then continuously evaporating, vaporizing and rectifying for purification;
(2) the method for continuously rectifying and purifying the isophthalonitrile provided by the invention can reduce the content of cyanobenzamide in the intermediate product from 2.55 wt% before refining to less than or equal to 0.12 wt%, greatly reduce the residue generation amount of a melting kettle in the production of downstream chlorothalonil, reduce the content of hexachlorobenzene in the downstream chlorothalonil product to 10ppm, improve the product quality of the chlorothalonil and relieve the environmental pressure;
(3) the method for continuously rectifying and purifying the isophthalonitrile provided by the invention can realize the continuous production of the isophthalonitrile by melting the isophthalonitrile and then continuously evaporating, vaporizing and rectifying the isophthalonitrile, and has the advantages of stable product quality and low operation cost.
Drawings
FIG. 1 is a schematic view of an apparatus used in a method for the continuous rectification and purification of isophthalonitrile provided in example 1 of the present invention.
In the figure: 1-feeding a metering pump; 2-melting the intermediate tank; 3-a scraper evaporator; 4-a first coke cutting kettle; 5-a second coke cutting kettle; 6-a rectifying tower; 7-a secondary condenser; 8-product condenser; 9-a product receiving kettle; 10-a material-beating metering pump; 11-a slag discharge groove; 12-a first product trap; 13-a second product trap; 14-a first vacuum pump; 15-second vacuum pump.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings. 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.
First, an embodiment
Example 1
The embodiment provides a method for continuously rectifying and purifying isophthalonitrile, which uses a device with a schematic diagram as shown in figure 1, and comprises the following steps:
(1) melting raw material of isophthalonitrile in a melting intermediate tank 2 with the temperature of 200 ℃, continuously evaporating and vaporizing the melted isophthalonitrile in a scraper evaporator 3 with the temperature of 280 ℃ and the vacuum degree of 0.095MPa, and intermittently and alternately collecting liquid-phase isophthalonitrile which is not completely vaporized in a first coke cutting kettle 4 and a second coke cutting kettle 5 with the temperature of 200 ℃;
the switching operation of the first coke cutting kettle 4 and the second coke cutting kettle 5 comprises the following steps:
(a) keeping valve V1, valve V2, valve V3, valve V4, valve V5, and valve V6 of fig. 1 closed before the scraper evaporator 3 is fed;
(b) opening a valve V1 and a valve V3, when the negative pressure in the first coke cutting kettle 4 is the same as the negative pressure in the scraper evaporator 3, the scraper evaporator 3 can continuously feed m-phthalonitrile raw material, and the liquid which is not completely vaporized in the scraper evaporator 3 flows into the first coke cutting kettle 4 under the action of gravity;
(c) when the liquid level in the first coke cutting kettle 4 reaches a set value, opening a valve V4, when the negative pressure in the second coke cutting kettle 5 is the same as the negative pressure in the scraper evaporator 3, opening a valve V6, starting to receive liquid by the second coke cutting kettle 5 at the moment, and then closing the valve V1 and the valve V3;
(d) opening a valve V2, pumping liquid in the first coke cutting kettle 4 into a distillation kettle of the intermittent distillation process, and closing a valve V2 after the liquid is pumped out;
(e) when the liquid level in the second coke cutting kettle 5 reaches a set value, opening a valve V1, when the negative pressure in the first coke cutting kettle 4 is the same as the negative pressure in the scraper evaporator 3, opening a valve V3, starting to receive liquid by the first coke cutting kettle 4 at the moment, and then closing the valve V4 and the valve V6;
(f) opening a valve V5, pumping liquid in the second coke cutting kettle 5 into a distillation kettle of the intermittent distillation process, and closing a valve V5 after the liquid is pumped out;
(g) repeating operations (c) - (f);
(2) rectifying the continuously evaporated and vaporized isophthalonitrile in a rectifying tower 6 with the vacuum degree of 0.095MPa to obtain purified isophthalonitrile, wherein the rectifying temperature in the rectifying process is 160 ℃, the stripping temperature is 280 ℃, the condensing temperature at the top of the tower is 160 ℃, and the reboiling temperature at the bottom of the tower is 280 ℃; carrying out secondary condensation on the non-condensable gas in the rectification process in a secondary condenser 7 at the temperature of 160 ℃, recovering a liquid-phase isophthalonitrile product subjected to secondary condensation, and regularly discharging and barreling high-boiling residues in the rectification process in a slag discharge groove 11 at the temperature of 280 ℃;
(3) receiving the isophthalonitrile products purified in the rectification process and secondarily condensed in the step (2) in a product receiving kettle 9 with the temperature of 160 ℃ and the vacuum degree of 0.095MPa, slicing the received isophthalonitrile products or introducing the received isophthalonitrile products into a chlorothalonil workshop, carrying out secondary condensation on gas phases which are not completely condensed in the receiving process in a product condenser 8 with the temperature of 160 ℃, and recovering liquid-phase isophthalonitrile products which are condensed again;
(4) and (4) trapping the gas-phase isophthalonitrile which is not completely condensed in the secondary condensation in the step (3) in a first product trap 12 and a second product trap 13 with the temperature of 60 ℃ and the vacuum degree of 0.095MPa to obtain a powder isophthalonitrile product.
The purity of the isophthalonitrile product prepared by the method provided by the embodiment is 99.85 wt%, the molar yield can reach 98.5%, and the isophthalonitrile prepared by the embodiment is used for downstream production of chlorothalonil, so that the hexachlorobenzene content in the chlorothalonil product can be reduced to 10ppm, and the product quality of the chlorothalonil is improved.
Example 2
The embodiment provides a method for continuously rectifying and purifying isophthalonitrile, which has the same process steps as those in embodiment 1, and has the same process operation parameters as those in embodiment 1 except that the vacuum degrees of the scraper evaporator 3, the rectifying tower 6, the product receiving kettle 9, the first product catcher 12 and the second product catcher 13 are changed to 0.09 MPa.
Example 3
The embodiment provides a method for continuously rectifying and purifying isophthalonitrile, which has the same process steps as those in embodiment 1, and has the same process operation parameters as those in embodiment 1 except that the vacuum degrees of a scraper evaporator 3, a rectifying tower 6, a product receiving kettle 9, a first product catcher 12 and a second product catcher 13 are changed to 0.07 MPa.
Example 4
The embodiment provides a method for continuously rectifying and purifying isophthalonitrile, which has the same process steps as those in the embodiment 1, and the other process operation parameters are the same as those in the embodiment 1 except that the temperature of a condenser at the top of a rectifying tower 6 is 200 ℃, the temperature of the lower section of a tower body is 260 ℃, the temperature of the upper section of the tower body is 200 ℃, and the temperature of a reboiler at the bottom of the tower is 260 ℃.
Example 5
The embodiment provides a method for continuously rectifying and purifying isophthalonitrile, which has the same process steps as those in the embodiment 1, and the other process operation parameters are the same as those in the embodiment 1 except that the temperature of a condenser at the top of a rectifying tower 6 is 180 ℃, the temperature of the lower section of a tower body is 300 ℃, the temperature of the upper section of the tower body is 180 ℃, and the temperatures of a reboiler and a slag discharge groove at the bottom of the tower are 300 ℃.
Example 6
This example provides a method for the continuous rectification and purification of isophthalonitrile, which comprises the same process steps as those in example 1, except that the temperature of the scraper evaporator 3 is 230 ℃, and the temperatures of the secondary condenser 7, the product condenser 8 and the product receiving tank 9 are 200 ℃, and the other process operation parameters are the same as those in example 1.
Example 7
The process steps of the method are the same as those of the embodiment 1, except that the temperature of the scraper evaporator 3 is 300 ℃, the temperatures of the secondary condenser 7, the product condenser 8 and the product receiving kettle 9 are 180 ℃, and the temperatures of the first product catcher 12 and the second product catcher 13 are 40 ℃, and the process operation parameters are the same as those of the embodiment 1.
Example 8
The embodiment provides a method for continuously rectifying and purifying isophthalonitrile, which comprises the same process steps as those in embodiment 1, wherein the process operation parameters are the same as those in embodiment 1 except that the temperature of a melting intermediate tank 2 is 160 ℃, the temperatures of a scraper evaporator 3 and a slag discharge tank 11 are 230 ℃, the temperatures of a secondary condenser 7, a product condenser 8 and a product receiving kettle 9 are 200 ℃, the temperatures of a first coke cutting kettle 4 and a second coke cutting kettle 5 are 160 ℃, the temperatures of a first product catcher 12 and a second product catcher 13 are 100 ℃, and all vacuum degrees are 0.098 MPa.
Example 9
The process steps are the same as those in example 1 except that the temperature of the melting intermediate tank 2 is 250 ℃, the temperature of a reboiler at the bottom of the rectifying tower 6 is 230 ℃, the temperatures of the first coke cutting kettle 4 and the second coke cutting kettle 5 are 250 ℃, and the other process operation parameters are the same as those in example 1.
Second, comparative example
Comparative example 1
The comparative example provides a method for purifying isophthalonitrile, which is different from the method in example 1 only in that the isophthalonitrile raw material is not subjected to continuous evaporation operation, and the isophthalonitrile melted in a melting intermediate tank is directly fed into a rectifying tower for rectification and purification, and the rest is the same as that in example 1, and the method specifically comprises the following steps:
(1) melting an isophthalonitrile raw material in a melting intermediate tank 2 at the temperature of 200 ℃, and directly introducing the melted isophthalonitrile into a rectifying tower 6 for rectification and purification;
the operation steps and process parameters in step (2), step (3) and step (4) were the same as in example 1.
Comparative example 2
The comparative example provides a method for purifying isophthalonitrile, the remaining steps and process parameters are the same as those of the example 1 except that the rectification process and corresponding steps in the step (2) of the example 1 are omitted, and the method specifically comprises the following steps:
(1) melting raw material of isophthalonitrile in a melting intermediate tank 2 with the temperature of 200 ℃, continuously evaporating and vaporizing the melted isophthalonitrile in a scraper evaporator 3 with the temperature of 280 ℃ and the vacuum degree of 0.095MPa, and intermittently and alternately collecting liquid-phase isophthalonitrile which is not completely vaporized in a first coke cutting kettle 4 and a second coke cutting kettle 5 with the temperature of 200 ℃; wherein, the switching operation steps of the first coke cutting kettle 4 and the second coke cutting kettle 5 are the same as that of the embodiment 1;
(2) directly introducing the continuously evaporated and vaporized isophthalonitrile into a secondary condenser 7 with the temperature of 160 ℃ for condensation to obtain a condensed liquid-phase isophthalonitrile product;
(3) receiving the condensed isophthalonitrile product in the step (2) in a product receiving kettle 9 with the temperature of 160 ℃ and the vacuum degree of 0.095MPa, slicing the received isophthalonitrile product or introducing the received isophthalonitrile product into a chlorothalonil workshop, carrying out secondary condensation on gas phase which is not completely condensed in the receiving process in a product condenser 8 with the temperature of 160 ℃, and recovering a secondary condensed liquid-phase isophthalonitrile product;
(4) and (4) trapping the gas-phase isophthalonitrile which is not completely condensed in the secondary condensation in the step (3) in a first product trap 12 and a second product trap 13 with the temperature of 60 ℃ and the vacuum degree of 0.095MPa to obtain a powder isophthalonitrile product.
In examples 1 to 9 and comparative examples 1 to 2 provided by the present invention, the isophthalonitrile raw material was treated, and the resulting isophthalonitrile product and the recovery rate of isophthalonitrile were analyzed, and the analysis results are shown in table 1.
TABLE 1
From table 1, the following points can be seen:
(1) it can be seen from the comprehensive examples 1 to 9 that the purity of the isophthalonitrile obtained by the isophthalonitrile continuous rectification and purification method provided by the invention is not less than 99.82 wt%, the content of the isophthalonitrile is not more than 0.12 wt%, and the content of the terephthalonitrile is only 0.04 wt%, so that the content of hexachlorobenzene in downstream chlorothalonil is reduced to 10ppm, and the molar yield of isophthalonitrile is not less than 95.6%, which indicates that the isophthalonitrile continuous rectification and purification method provided by the invention can obtain an isophthalonitrile product with high purity and high recovery rate by the operations of melting, evaporation and vaporization of an isophthalonitrile raw material and rectification and purification, thereby significantly reducing the content of the cyanobenzoamide in the intermediate product, reducing the content of hexachlorobenzene in the downstream chlorothalonil product, and relieving the environmental pressure;
(2) by combining the example 1 and the comparative example 1, it can be seen that, in the example 1, through continuous evaporation and vaporization in the scraper evaporator, compared with the comparative example 1 in which liquid-phase phthalonitrile is directly rectified and purified, the isophthalonitrile product obtained in the example 1 has the purity of 99.85 wt% and the molar recovery rate of 98.5%, and in the comparative example 1, the isophthalonitrile product has the purity of only 99.65 wt% and the molar yield of only 95.0%, so that the invention ensures the feed components in the rectification process, makes the rectification and purification process more stable, and improves the purity and yield of the final isophthalonitrile product;
(3) it can be seen from the combination of example 1 and comparative example 2 that, by performing the rectification purification operation after the vaporization of isophthalonitrile in example 1, the purity of the isophthalonitrile product obtained in example 1 was 99.85 wt%, the content of isophthalonitrile therein was only 0.09 wt%, the content of terephthalonitrile therein was only 0.04 wt%, and the molar recovery of the isophthalonitrile product was 98.5 wt%, while the purity of the product obtained in comparative example 2 was only 99.51 wt%, the content of isophthalonitrile therein was up to 0.32 wt%, the content of terephthalonitrile therein was up to 0.15 wt%, and the molar recovery of the isophthalonitrile product was 98.3%, as compared to the case where the vapor phase of isophthalonitrile directly vaporized by the condensation collection of the vapor phase of isophthalonitrile by the vaporization of isophthalonitrile therein was directly collected, thereby illustrating that the present invention can better separate isophthalonitrile from impurities in the raw materials by adding the rectification purification operation after the vaporization of isophthalonitrile, the content of the intermediate cyanobenzamide in the product is reduced, and the isophthalonitrile product with higher purity is obtained.
In conclusion, the isophthalonitrile prepared by the isophthalonitrile continuous rectification and purification method provided by the invention has the product purity of more than or equal to 99.82 wt%, wherein the content of the m-cyanobenzamide is less than or equal to 0.12 wt%, so that the content of hexachlorobenzene in downstream chlorothalonil products is reduced to 10ppm, meanwhile, the molar yield of the m-phthalonitrile is more than or equal to 95.6%, the content of the m-cyanobenzamide in the m-phthalonitrile products is effectively reduced, and the method can be used for stably and continuously producing the isophthalonitrile, is low in production cost and has higher industrial application value.
The applicant declares that the present invention illustrates the detailed structural features of the present invention through the above embodiments, but the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must be implemented depending on the above detailed structural features. It should be understood by those skilled in the art that any modifications of the present invention, equivalent substitutions of selected components of the present invention, additions of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.
Claims (10)
1. The method for continuously rectifying and purifying the isophthalonitrile is characterized by comprising the following steps of:
(1) melting an isophthalonitrile raw material, and continuously evaporating and vaporizing the melted isophthalonitrile;
(2) and rectifying the continuously evaporated and vaporized isophthalonitrile to obtain purified isophthalonitrile.
2. The method according to claim 1, wherein in the step (1), the melting process is heated by using heat transfer oil;
preferably, the temperature of the heat conducting oil in the melting process is 160-250 ℃, and preferably 180-200 ℃.
3. The method according to claim 1 or 2, wherein the continuous evaporative vaporization process in step (1) is heated with a heat transfer oil;
preferably, the temperature of the heat conduction oil in the continuous evaporation and vaporization process is 230-300 ℃, and preferably 260-280 ℃;
preferably, the vacuum degree in the continuous evaporation and vaporization process is 0.07-0.098 MPa, and preferably 0.09-0.095 MPa;
preferably, the liquid phase isophthalonitrile which is not completely vaporized in the continuous evaporative vaporization process is collected;
preferably, the collection process adopts heat-conducting oil for heating;
preferably, the temperature of the heat conducting oil in the collection process is 160-250 ℃, and preferably 180-200 ℃.
4. The method according to any one of claims 1 to 3, wherein the rectification process in step (2) is heated by using heat transfer oil;
preferably, the rectification temperature in the rectification process is 160-200 ℃, and preferably 160-180 ℃;
preferably, the stripping temperature in the rectification process is 230-300 ℃, and preferably 260-280 ℃;
preferably, the condensation temperature at the top of the tower in the rectification process is 160-200 ℃, and preferably 160-180 ℃;
preferably, the reboiling temperature of the tower bottom in the rectification process is 230-300 ℃, and preferably 260-280 ℃;
preferably, the vacuum degree in the rectification process is 0.07-0.098 MPa, and preferably 0.09-0.095 MPa.
5. The method according to any one of claims 1 to 4, characterized in that the noncondensable gas in the rectification process in the step (2) is subjected to secondary condensation, and a secondary condensed liquid-phase isophthalonitrile product is recovered;
preferably, the secondary condensation process adopts heat transfer oil for heat exchange;
preferably, the temperature of the heat conducting oil in the secondary condensation process is 160-200 ℃, and preferably 160-180 ℃.
6. The method according to any one of claims 1 to 5, wherein in the step (2), the high-boiling residues of the rectification process are periodically discharged and barreled;
preferably, the high-boiling substance is m-cyanobenzamide and/or phthalimide;
preferably, the slag discharging process adopts heat conducting oil for heating;
preferably, the temperature of the heat conducting oil in the deslagging process is 230-300 ℃, and preferably 260-280 ℃.
7. The method according to any one of claims 1 to 6, further comprising, after the step (2), a step (3):
receiving the isophthalonitrile product purified in the step (2);
preferably, receiving the m-phthalonitrile product purified by the rectification process in the step (2) and/or secondarily condensed;
preferably, the receiving process adopts heat conducting oil for heating;
preferably, the temperature of the heat conduction oil in the receiving process is 160-200 ℃, and preferably 160-180 ℃;
preferably, the vacuum degree of the receiving process is 0.07-0.098 MPa, and preferably 0.09-0.095 MPa.
8. The method of claim 7, wherein the isophthalonitrile product received in step (3) is sliced or passed to a chlorothalonil plant;
preferably, the gas phase which is not completely condensed in the receiving process of the step (3) is subjected to secondary condensation, and a secondary condensed liquid-phase phthalonitrile product is recovered.
9. The method according to any one of claims 7 to 8, characterized in that the gas-phase isophthalonitrile which is not completely condensed in the recondensation in the step (3) is collected to obtain a powder isophthalonitrile product;
preferably, the capture process employs water or cold air for condensation;
preferably, the temperature in the trapping process is 40-100 ℃, and preferably 50-70 ℃;
preferably, the vacuum degree of the trapping process is 0.07-0.098 MPa, and preferably 0.09-0.095 MPa.
10. A method according to any one of claims 1 to 9, characterized in that the method comprises the steps of:
(1) melting an isophthalonitrile raw material at 160-250 ℃, continuously evaporating and vaporizing the melted isophthalonitrile at 230-300 ℃ and 0.07-0.098 MPa, and collecting liquid-phase isophthalonitrile which is not completely vaporized at 160-250 ℃;
(2) rectifying the continuously evaporated and vaporized isophthalonitrile under the pressure of 0.07-0.098 MPa to obtain purified isophthalonitrile, wherein the rectification temperature in the rectification process is 160-200 ℃, the stripping temperature is 230-300 ℃, the condensation temperature at the top of the tower is 160-200 ℃, and the reboiling temperature at the bottom of the tower is 230-300 ℃; carrying out secondary condensation on the non-condensable gas in the rectification process at the temperature of 160-200 ℃, recovering a liquid-phase isophthalonitrile product subjected to secondary condensation, and periodically discharging and barreling high-boiling-point substances in the rectification process at the temperature of 230-300 ℃;
(3) and (3) receiving the m-phthalonitrile product purified and secondarily condensed in the rectification process in the step (2) under the conditions of 160-200 ℃ and 0.07-0.098 MPa, re-condensing the gas phase which is not completely condensed in the receiving process, and recovering the re-condensed liquid-phase phthalonitrile product.
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| CN111233708A (en) * | 2020-03-12 | 2020-06-05 | 江苏维尤纳特精细化工有限公司 | Isophthalonitrile refining process with safe feeding and smooth slag discharge |
| CN111440092A (en) * | 2020-03-30 | 2020-07-24 | 江苏维尤纳特精细化工有限公司 | Safe and automatic m-phthalonitrile refining process |
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