CN112661651A - Purification method and purification device of 3, 4-dichloronitrobenzene - Google Patents
Purification method and purification device of 3, 4-dichloronitrobenzene Download PDFInfo
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- NTBYINQTYWZXLH-UHFFFAOYSA-N 1,2-dichloro-4-nitrobenzene Chemical compound [O-][N+](=O)C1=CC=C(Cl)C(Cl)=C1 NTBYINQTYWZXLH-UHFFFAOYSA-N 0.000 title claims abstract description 62
- 238000000034 method Methods 0.000 title claims abstract description 61
- 238000000746 purification Methods 0.000 title claims abstract description 58
- 238000002425 crystallisation Methods 0.000 claims abstract description 231
- 230000008025 crystallization Effects 0.000 claims abstract description 231
- 238000002844 melting Methods 0.000 claims abstract description 171
- 230000008018 melting Effects 0.000 claims abstract description 171
- 210000004243 sweat Anatomy 0.000 claims abstract description 111
- 239000013078 crystal Substances 0.000 claims abstract description 91
- 238000006396 nitration reaction Methods 0.000 claims abstract description 58
- RFFLAFLAYFXFSW-UHFFFAOYSA-N 1,2-dichlorobenzene Chemical compound ClC1=CC=CC=C1Cl RFFLAFLAYFXFSW-UHFFFAOYSA-N 0.000 claims abstract description 34
- 238000001816 cooling Methods 0.000 claims abstract description 30
- 239000002253 acid Substances 0.000 claims abstract description 25
- 239000002994 raw material Substances 0.000 claims description 112
- 238000003860 storage Methods 0.000 claims description 72
- 230000035900 sweating Effects 0.000 claims description 70
- 239000012670 alkaline solution Substances 0.000 claims description 12
- 238000006386 neutralization reaction Methods 0.000 claims description 9
- 238000006243 chemical reaction Methods 0.000 claims description 7
- 239000003795 chemical substances by application Substances 0.000 claims description 4
- 238000004321 preservation Methods 0.000 claims description 4
- 238000003491 array Methods 0.000 claims description 3
- 239000000155 melt Substances 0.000 claims description 2
- 239000000126 substance Substances 0.000 claims description 2
- 238000007670 refining Methods 0.000 claims 1
- 238000004519 manufacturing process Methods 0.000 abstract description 15
- 230000008569 process Effects 0.000 abstract description 15
- 239000002904 solvent Substances 0.000 abstract description 5
- 230000007613 environmental effect Effects 0.000 abstract description 3
- 238000010438 heat treatment Methods 0.000 description 41
- 238000007599 discharging Methods 0.000 description 36
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 16
- 239000000463 material Substances 0.000 description 16
- UIIMBOGNXHQVGW-UHFFFAOYSA-M Sodium bicarbonate Chemical compound [Na+].OC([O-])=O UIIMBOGNXHQVGW-UHFFFAOYSA-M 0.000 description 14
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 14
- 238000005086 pumping Methods 0.000 description 11
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 8
- 229910017604 nitric acid Inorganic materials 0.000 description 8
- 230000000630 rising effect Effects 0.000 description 8
- 229910000030 sodium bicarbonate Inorganic materials 0.000 description 7
- 235000017557 sodium bicarbonate Nutrition 0.000 description 7
- 239000000243 solution Substances 0.000 description 7
- 239000007788 liquid Substances 0.000 description 6
- 239000007791 liquid phase Substances 0.000 description 6
- CMVQZRLQEOAYSW-UHFFFAOYSA-N 1,2-dichloro-3-nitrobenzene Chemical compound [O-][N+](=O)C1=CC=CC(Cl)=C1Cl CMVQZRLQEOAYSW-UHFFFAOYSA-N 0.000 description 5
- SDYWXFYBZPNOFX-UHFFFAOYSA-N 3,4-dichloroaniline Chemical compound NC1=CC=C(Cl)C(Cl)=C1 SDYWXFYBZPNOFX-UHFFFAOYSA-N 0.000 description 4
- 238000005265 energy consumption Methods 0.000 description 4
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- 238000009835 boiling Methods 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 2
- BWHMMNNQKKPAPP-UHFFFAOYSA-L potassium carbonate Chemical compound [K+].[K+].[O-]C([O-])=O BWHMMNNQKKPAPP-UHFFFAOYSA-L 0.000 description 2
- LOCWBQIWHWIRGN-UHFFFAOYSA-N 2-chloro-4-nitroaniline Chemical compound NC1=CC=C([N+]([O-])=O)C=C1Cl LOCWBQIWHWIRGN-UHFFFAOYSA-N 0.000 description 1
- 238000007098 aminolysis reaction Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000012295 chemical reaction liquid Substances 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 238000010924 continuous production Methods 0.000 description 1
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- 230000004048 modification Effects 0.000 description 1
- 230000003472 neutralizing effect Effects 0.000 description 1
- 150000002894 organic compounds Chemical class 0.000 description 1
- 239000011736 potassium bicarbonate Substances 0.000 description 1
- 229910000028 potassium bicarbonate Inorganic materials 0.000 description 1
- 235000015497 potassium bicarbonate Nutrition 0.000 description 1
- 229910000027 potassium carbonate Inorganic materials 0.000 description 1
- 235000011181 potassium carbonates Nutrition 0.000 description 1
- TYJJADVDDVDEDZ-UHFFFAOYSA-M potassium hydrogencarbonate Chemical compound [K+].OC([O-])=O TYJJADVDDVDEDZ-UHFFFAOYSA-M 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 229910000029 sodium carbonate Inorganic materials 0.000 description 1
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Abstract
The invention relates to a method and a device for purifying 3, 4-dichloronitrobenzene. The purification method provided by the invention comprises the following steps: a nitration step: reacting o-dichlorobenzene with mixed acid to obtain a nitration product; a first-stage melting crystallization step: melting the nitration product, and then cooling and crystallizing to obtain a primary crystallization product; and, the primary crystallized product is melted again to sweat, and primary sweat and 3, 4-dichloronitrobenzene crystals are obtained. The process of the invention does not need to add solvent, has simple process, good product yield and high purity, and has obvious advantages of safety and environmental protection compared with the traditional process; moreover, the purification device has simple structure and high production efficiency.
Description
Technical Field
The invention belongs to the technical field of organic compound purification, and particularly relates to a purification method and a purification device for 3, 4-dichloronitrobenzene.
Background
The 3, 4-dichloronitrobenzene is an important organic intermediate, can be used for preparing 2-chloro-4-nitroaniline by aminolysis, and can be used for preparing 3, 4-dichloroaniline by reduction, and the structural formula of the 3, 4-dichloroaniline is shown as (I), the melting point of the 3, 4-dichloroaniline is 43 ℃, the boiling point of the 3, 4-dichloronitrobenzene is 255-256 ℃, and the molecular weight of the 3, 4-dichloroaniline is 192.
3, 4-dichloronitrobenzene is produced by the nitration of o-dichlorobenzene, the nitration product of which is inevitably accompanied by the formation of 2, 3-dichloronitrobenzene, and in practice only the purification of 3, 4-dichloronitrobenzene to > 99% is of industrial utility. The traditional purification method mainly comprises a solvent method and a rectification method, wherein the solvent method has the disadvantages of high process risk, low yield, low purity and difficulty in realizing automation; if a conventional rectification method is adopted for separation, the boiling point of the 3, 4-dichloronitrobenzene is higher and is close to the boiling point of the 2, 3-dichloronitrobenzene at 257-258 ℃, so that the required theoretical plate number is large, the rectification efficiency is low, and the energy consumption is high.
In view of the above, it is of great significance to find a purification method which is green, environment-friendly, safe and can ensure the quality to replace the traditional process.
Disclosure of Invention
Problems to be solved by the invention
In view of the problems in the prior art, the invention firstly provides a method for purifying 3, 4-dichloronitrobenzene. The purification method provided by the invention can obtain high-purity 3, 4-dichloronitrobenzene.
Furthermore, the purification method of the invention is energy-saving and environment-friendly, has safe process and no three wastes and can realize continuous production.
Furthermore, the invention also provides a device for purifying the 3, 4-dichloronitrobenzene, and materials can be conveyed in a liquid manner in the whole process, thereby being beneficial to continuous automatic production.
Means for solving the problems
The invention provides a method for purifying 3, 4-dichloronitrobenzene, which comprises the following steps:
a nitration step: reacting o-dichlorobenzene with mixed acid to obtain a nitration product;
a first-stage melting crystallization step: melting the nitration product, and then cooling and crystallizing to obtain a primary crystallization product; and the number of the first and second electrodes,
and melting and sweating the primary crystallization product again to obtain primary sweat and 3, 4-dichloronitrobenzene crystals.
The purification method according to the present invention, wherein the purification method further comprises a secondary melt crystallization step; the secondary melting crystallization step comprises melting the primary sweat, cooling and crystallizing to obtain a secondary crystallization product; and the number of the first and second electrodes,
melting and sweating the secondary crystallization product again to obtain secondary sweat and primary raw material crystals; wherein
The primary raw material crystals can be mixed with the nitration product and subjected to the primary melt crystallization.
The purification method according to the present invention, wherein the purification method further comprises a three-stage melt crystallization step; the third-stage melting crystallization step comprises the steps of melting the second-stage sweat, cooling and crystallizing to obtain a third-stage crystallization product; and the number of the first and second electrodes,
melting and sweating the tertiary crystallization product again to obtain tertiary sweat and secondary raw material crystals; wherein
The secondary raw material crystals can be mixed with the primary sweat and subjected to the secondary melt crystallization.
According to the purification method, in the nitration step, the mixed acid is dropwise added into the o-dichlorobenzene at the temperature of 20-30 ℃, then the heat preservation reaction is carried out at the temperature of 55-60 ℃, and the nitration product is obtained after post-treatment.
The purification method according to the present invention, wherein the post-treatment comprises a step of performing a neutralization treatment with an alkaline solution; preferably, the concentration of an alkaline agent in the alkaline solution is 1-1.5 wt%, the temperature of the neutralization treatment is 50-60 ℃, and the usage amount of the alkaline solution is 2-3 times of the mass of the nitration product.
According to the purification method, in the primary melting crystallization step, the melting temperature is 55-60 ℃, the crystallization temperature is 25-30 ℃, and the crystallization time is 3.5-4.5 hours;
the temperature for remelting and sweating is 30-35 ℃, and the time for remelting and sweating is 0.5-1.5 hours;
preferably, the first-stage crystallization product is melted again for sweating by means of temperature rise, and more preferably, the temperature rise rate is 1-5 ℃/hour.
According to the purification method, in the secondary melting crystallization step, the melting temperature is 45-55 ℃, the crystallization temperature is 17-22 ℃, and the crystallization time is 3.5-4.5 hours;
the temperature for remelting and sweating is 24-29 ℃, and the time for remelting and sweating is 0.5-1.5 hours;
preferably, the secondary crystallization product is melted again for sweating by means of temperature rise, and more preferably, the temperature rise rate is 1-5 ℃/hour.
According to the purification method, in the three-stage melting crystallization step, the melting temperature is 30-35 ℃, the crystallization temperature is 9-14 ℃, and the crystallization time is 4.0-5.0 hours;
the temperature for remelting and sweating is 15-20 ℃, and the time for remelting and sweating is 0.5-1.5 hours;
preferably, the tertiary crystallization product is melted again for sweating by means of temperature rise, and more preferably, the temperature rise rate is 0.5-4 ℃/hour.
The invention also provides a purification device for implementing the purification method, wherein the purification device comprises at least one melt crystallization kettle.
According to the purification device provided by the invention, the purification device comprises a first-stage melting crystallization kettle, a second-stage melting crystallization kettle and a third-stage melting crystallization kettle which are sequentially connected; wherein the content of the first and second substances,
the discharge port of the second-stage melting crystallization kettle is connected with the feed inlet of the first-stage melting crystallization kettle, and the discharge port of the third-stage melting crystallization kettle is connected with the feed inlet of the second-stage melting crystallization kettle.
According to the purification device, a plurality of groups of tube array structures are arranged inside the melting crystallization kettle;
preferably, the diameter of the tube array is 40-50 mm, and the distance between the tube array and the tube array is 20-30 mm.
According to the purification device, a heat source medium and a cold source medium are inserted into the outer jackets of the tubes.
According to the purification apparatus of the present invention, the purification apparatus further comprises at least one storage tank.
ADVANTAGEOUS EFFECTS OF INVENTION
The method for purifying 3, 4-dichloronitrobenzene provided by the invention can obtain high-purity 3, 4-dichloronitrobenzene, and the yield is obviously improved.
Furthermore, the method for purifying 3, 4-dichloronitrobenzene provided by the invention does not need to add a solvent, has simple process, and has obvious advantages of safety, environmental protection and low energy consumption compared with the traditional process.
Furthermore, the purification device for 3, 4-dichloronitrobenzene provided by the invention has a simple structure, the materials are conveyed in a liquid mode in the whole production process, the continuous automatic production is facilitated, and the production efficiency is high.
Drawings
FIG. 1 is a schematic structural view of a 3, 4-dichloronitrobenzene purification device of the present invention;
description of the reference numerals
1.2, 3-first-stage melting crystallization kettle; 4-second-stage melting crystallization kettle; 5-three-stage melting crystallization kettle; 6-primary raw material storage tank; 7-a secondary raw material storage tank; 8-finished product storage tank; 9-three-stage raw material storage tanks; 10-a tailings storage tank; 11-a first material transfer pump; 12-a second material transfer pump; 13-a heat source medium; 14-Cold Source Medium.
Detailed Description
Various exemplary embodiments, features and aspects of the invention will be described in detail below. The word "exemplary" is used exclusively herein to mean "serving as an example, embodiment, or illustration. Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments.
Furthermore, in the following detailed description, numerous specific details are set forth in order to provide a better understanding of the present invention. It will be understood by those skilled in the art that the present invention may be practiced without some of these specific details. In other instances, methods, means, devices and steps which are well known to those skilled in the art have not been described in detail so as not to obscure the invention.
< first aspect >
The invention provides a method for purifying 3, 4-dichloronitrobenzene, which comprises the following steps:
a nitration step: reacting o-dichlorobenzene with mixed acid to obtain a nitration product;
a first-stage melting crystallization step: melting the nitration product, and then cooling and crystallizing to obtain a primary crystallization product; and the number of the first and second electrodes,
and melting and sweating the primary crystallization product again to obtain primary sweat and 3, 4-dichloronitrobenzene crystals.
The 3, 4-dichloronitrobenzene crystal with high purity can be obtained by the purification method of the 3, 4-dichloronitrobenzene provided by the invention.
< nitration step >
The invention obtains the nitration product by reacting o-dichlorobenzene with mixed acid. In some preferred embodiments of the invention, in the nitration step, the mixed acid is dropwise added into o-dichlorobenzene at a temperature of 20-30 ℃, then the heat preservation reaction is carried out at a temperature of 55-60 ℃ for 5-7 hours, after the heat preservation reaction is carried out for 5-7 hours, the reaction can be carried out to the end point, and the nitration product is obtained after post-treatment. In order to make the reaction mild and avoid over-nitration, the invention adopts a method of dripping mixed acid into o-dichlorobenzene and controls the temperature in the dripping process to be 20-30 ℃.
Specifically, the mixed acid is selected from but not limited to a mixture of nitric acid and sulfuric acid, wherein the mass ratio of the nitric acid to the sulfuric acid is 1: 2-4.
As for the post-treatment, in the present invention, the post-treatment includes a step of performing a neutralization treatment with an alkaline solution; by performing the neutralization treatment using an alkaline solution, the excess acid in the nitration product can be further removed. Preferably, in order to make the neutralization treatment more effectively, the concentration of the alkaline agent in the alkaline solution is 1-1.5 wt%, the temperature of the neutralization treatment is 50-60 ℃, and the usage amount of the alkaline solution is 2-3 times of the mass of the nitration product.
Specifically, the alkaline agent may be selected from, but not limited to, one or a combination of two or more of baking soda, sodium hydroxide, potassium carbonate, sodium carbonate, potassium bicarbonate, and the like, preferably baking soda.
In some embodiments, to facilitate the first-order melt crystallization, the post-treatment step comprises: and (3) firstly layering the reaction solution after nitration to remove an acid water layer, namely a mixed liquid layer of acid and water, then adding an alkaline solution for neutralization, and finally layering to remove the water layer to obtain a nitration product.
Further, in the invention, in the nitration product, the purity of the liquid phase of the crude nitration product 3, 4-dichloronitrobenzene is 91-93%, and the purity of the liquid phase of the 2, 3-dichloronitrobenzene is 6-7.5%.
< first stage melt crystallization step >
In the first-stage melting crystallization step, melting the nitrified product, and then cooling and crystallizing to obtain a first-stage crystallized product; and, the primary crystallized product is melted again to sweat, resulting in primary sweat and 3, 4-dichloronitrobenzene crystals. The purity of the 3, 4-dichloronitrobenzene crystal obtained by the first-stage melting crystallization can reach more than 99 percent.
In some specific embodiments, in order to obtain 3, 4-dichloronitrobenzene crystals with more excellent performance, the primary melt crystallization step comprises: firstly, melting a nitration product at the temperature of 55-60 ℃, and then cooling to 25-30 ℃ for crystallization, wherein the crystallization time is 3.5-4.5 hours, so as to obtain a primary crystallization product; and then melting and sweating the primary crystallization product again at the temperature of 30-35 ℃, and controlling the time of melting and sweating again to be 0.5-1.5 hours, thus obtaining the high-purity 3, 4-dichloronitrobenzene crystal and primary sweat.
In some preferred embodiments of the present invention, in order to further improve the purity of the 3, 4-dichloronitrobenzene crystal, the primary crystallization product is melted again and sweated by slowly raising the temperature; preferably, the temperature rise rate is 1-5 ℃/hour.
In the first-stage melting crystallization step, after the first-stage crystallization product is melted again to sweat, the first-stage sweat containing 3, 4-dichloronitrobenzene is obtained after the high-purity 3, 4-dichloronitrobenzene crystals are obtained. Specifically, when the temperature for remelting and sweating is 30-35 ℃, the mass of the obtained primary sweat can be 35-45% of that of the nitration product.
Furthermore, the purity of the 3, 4-dichloronitrobenzene liquid phase in the primary sweat is 85-88%, and the purity of the 2, 3-dichloronitrobenzene liquid phase is 11-14%, so that the secondary melting crystallization can be carried out on the primary sweat for further improving the total yield of the 3, 4-dichloronitrobenzene.
< Secondary melting crystallization step >
The purification method of 3, 4-dichloronitrobenzene provided by the invention also comprises a secondary melting crystallization step, wherein the secondary melting crystallization step comprises the steps of melting primary sweat, cooling and crystallizing to obtain a secondary crystallization product; and melting and sweating the secondary crystallization product again to obtain secondary sweat and primary raw material crystals. The primary raw material crystal can be mixed with a nitration product to be used as a primary raw material and subjected to primary melting crystallization, so that the 3, 4-dichloronitrobenzene contained in primary sweat is recovered and purified.
Furthermore, the melting temperature of the primary raw material crystal is 40-45 ℃, namely the primary raw material crystal can be melted at 40-45 ℃ and is mixed with a nitration product to be used as a primary raw material.
Specifically, in the secondary melting crystallization step, first-stage sweat is melted at 45-55 ℃, and then is cooled to 17-22 ℃ for crystallization, wherein the crystallization time is 3.5-4.5 hours, so that a secondary crystallization product is obtained; and then melting and sweating the secondary crystallization product again at the temperature of 24-29 ℃, and controlling the time of melting and sweating again to be 0.5-1.5 hours, thereby obtaining secondary sweat and primary raw material crystals.
In the invention, when the secondary crystallization product is at a temperature of 24-29 ℃, the mass of the primary sweat can be 35-45% of that of the primary raw material. The primary raw material can be primary sweat only or a mixture of the primary sweat and the molten primary raw material crystals.
In some preferred embodiments of the present invention, in order to perform the secondary melt crystallization step more efficiently, the secondary crystallization product may be melted again to sweat by slowly raising the temperature, preferably at a rate of 1 to 5 ℃/hr.
Furthermore, the purity of the liquid phase of the 3, 4-dichloronitrobenzene in the secondary sweat is 76-79%, and the purity of the liquid phase of the 2, 3-dichloronitrobenzene is 20-23%, so that the total yield of the 3, 4-dichloronitrobenzene is further improved, and the secondary sweat can be subjected to three-stage melting crystallization.
< three-stage melt crystallization step >
The invention provides a purification method of 3, 4-dichloronitrobenzene, which also comprises a third-stage melting crystallization step, wherein the third-stage melting crystallization step comprises the steps of melting second-stage sweat, cooling and crystallizing to obtain a third-stage crystallization product; and melting and sweating the tertiary crystallization product again to obtain tertiary sweat and secondary raw material crystals, wherein the secondary raw material crystals can be mixed with the primary sweat to be used as a secondary raw material and subjected to secondary melting and crystallization, so that the 3, 4-dichloronitrobenzene contained in the secondary sweat is recovered and purified.
Furthermore, the melting temperature of the secondary raw material crystal is 30-35 ℃, namely the secondary raw material crystal can be melted at 30-35 ℃ and is mixed with primary sweat to be used as a secondary raw material.
Specifically, in the third-stage melting crystallization step, melting secondary sweat serving as a third-stage raw material at 30-35 ℃, cooling to 9-14 ℃ for crystallization, wherein the crystallization time is 4.0-5.0 hours, and obtaining a third-stage crystallization product; and then melting and sweating the tertiary crystallization product again at the temperature of 15-20 ℃, and controlling the time of melting and sweating again to be 0.5-1.5 hours, thereby obtaining tertiary sweat and secondary raw material crystals.
In the invention, when the secondary crystallization product is at a temperature of 15-20 ℃, the mass of the secondary sweat can be 40-45% of the mass of the secondary raw material. The secondary raw material can be only secondary sweat or can be a mixture of the secondary sweat and the molten primary raw material crystals.
In some preferred embodiments of the present invention, in order to more efficiently perform the third-stage melt crystallization step, the third-stage crystallization product may be melted again to sweat by slowly raising the temperature, preferably at a rate of 0.5 to 4 ℃/hr.
In some preferred embodiments of the present invention, in the tertiary melt crystallization step, when the temperature of the secondary crystallization product is 15-20 ℃, the quality of the obtained tertiary sweat can be 55-70% of the quality of the secondary sweat, but in consideration of the energy consumption and efficiency problems in the purification process, the content of 3, 4-dichloronitrobenzene in the tertiary sweat is low, and the tertiary sweat is not suitable for melt crystallization treatment and can be separately collected for other treatment.
According to the method for purifying 3, 4-dichloronitrobenzene provided by the invention, 3, 4-dichloronitrobenzene with the purity of more than 99% can be obtained by carrying out three-stage melting crystallization on a nitration product obtained by reacting o-dichlorobenzene with mixed acid, and the yield is obviously improved; moreover, the purification method does not need to add a solvent, has simple process, and has obvious advantages of safety and environmental protection and low energy consumption compared with the traditional process.
< second aspect >
The present invention also provides a purification apparatus for carrying out the purification method according to < first aspect >, the purification apparatus comprising at least one melt crystallization kettle, and the nitration product is melted, cooled and crystallized to obtain a primary crystallization product; and, the primary crystalline product is melted again to sweat, and 3, 4-dichloronitrobenzene crystals with purity of more than 99 percent are obtained.
In the primary melt crystallization step, it is considered that, in addition to obtaining high-purity 3, 4-dichloronitrobenzene crystals, primary sweat containing 3, 4-dichloronitrobenzene is obtained. In order to further improve the total yield of the 3, 4-dichloronitrobenzene, the first-level sweat can be subjected to second-level melting crystallization.
In some preferred embodiments, the purification apparatus provided by the present invention comprises a first-stage melting crystallization kettle, a second-stage melting crystallization kettle and a third-stage melting crystallization kettle which are connected in sequence, wherein a feed inlet of the second-stage melting crystallization kettle is connected with a discharge outlet of the first-stage melting crystallization kettle, and a feed inlet of the third-stage melting crystallization kettle is connected with a discharge outlet of the second-stage melting crystallization kettle, so that the purity and yield of 3, 4-dichloronitrobenzene can be improved.
In some preferred embodiments, a plurality of groups of tube array structures are arranged in the melting crystallization kettle, and a heat source medium and a cold source medium are inserted into a jacket on the outer side of the tubes, so that heat exchange can be better realized in the melting crystallization process; preferably, the diameter of the tube array is 40-50 mm, and the distance between the tube arrays is 20-30 mm.
To facilitate material transfer between the melt crystallization vessels, in some preferred embodiments, the purification apparatus further comprises at least one storage tank; preferably, this purification device sets up one-level raw materials storage jar at one-level melting crystallization cauldron feed inlet, sets up second grade raw materials storage jar between one-level melting crystallization cauldron discharge gate and second grade melting crystallization cauldron feed inlet, sets up tertiary raw materials storage jar between second grade melting crystallization cauldron discharge gate and tertiary melting crystallization cauldron feed inlet, simultaneously, still sets up finished product storage jar at one-level melting crystallization cauldron discharge gate, still sets up the tails storage jar at tertiary melting crystallization cauldron discharge gate.
Specifically, as shown in fig. 1, the purification apparatus includes three primary melt crystallization kettles 1, 2, and 3, a primary raw material storage tank 6, a secondary raw material storage tank 7, and a finished product storage tank 8. The discharge ports of the three first-stage melting crystallization kettles 1, 2 and 3 are respectively connected with the feed ports of a second-stage raw material storage tank 7 and a finished product storage tank 8, the first-stage raw material storage tank collects first-stage sweat, and the finished product storage tank collects 3, 4-dichloronitrobenzene.
As shown in fig. 1, a feed inlet of the second-stage melting crystallization kettle 4 is connected with a second-stage raw material storage tank 7, a discharge outlet of the second-stage melting crystallization kettle is connected with a third-stage raw material storage tank 9, and second-stage sweat is collected; meanwhile, a discharge port of the second-stage melting crystallization kettle 4 is connected with a first material conveying pump 11, the first material conveying pump 11 is connected with the first-stage raw material storage tank 6, and the first-stage raw material crystals are conveyed to the first-stage raw material storage tank 6.
As shown in fig. 1, a feed inlet of the third-stage melting crystallization kettle 5 is connected with a third-stage raw material storage tank 9, a discharge outlet of the third-stage melting crystallization kettle is connected with a tailing storage tank 10, and third-stage sweat is collected; meanwhile, a discharge port of the third-stage melting crystallization kettle 5 is connected with a second material conveying pump 12, the second material conveying pump 12 is connected with the second-stage raw material storage tank 7, and the second-stage raw material crystals are conveyed to the second-stage raw material storage tank 7.
As shown in fig. 1, a plurality of sets of tube array structures are arranged in three first-stage melting crystallization kettles 1, 2 and 3, a second-stage melting crystallization kettle 4 and a third-stage melting crystallization kettle 5, the tube array diameter is 40-50 mm, the tube array distance is 20-30 mm, materials are arranged on the inner sides of the tube arrays, and a heat source medium 13 and a cold source medium 14 are simultaneously connected to an outer jacket; and (5) insulating all pipelines.
The specific working process of the purification device is as follows: firstly, removing acid water layers from nitration product reaction liquid in a layering mode, neutralizing with alkaline solution to obtain nitration product, collecting the nitration product in a primary raw material storage tank 6, sequentially placing the nitration product in primary melting crystallization kettles 1, 2 and 3, cooling to a primary crystallization temperature, opening a sweat discharging valve after the crystallization time is up, slowly heating to a target temperature for sweating and liquid discharging, collecting the obtained primary sweat in a secondary raw material storage tank 7, heating to 50-55 ℃ after the sweating is finished, melting residual crystals in the primary melting crystallization kettles 1, 2 and 3, and placing the crystals in a finished product storage tank 8 to obtain the finished product of the 3, 4-dichloronitrobenzene.
And then, collecting the primary sweat in the secondary raw material storage tank 7 to a target amount, putting the primary sweat in a secondary melting crystallization kettle 4, cooling to a secondary crystallization temperature, opening a sweat discharging valve after the crystallization time is up, slowly heating to the target temperature for sweating and discharging liquid, collecting the obtained secondary sweat in a tertiary raw material storage tank 9, heating to 40-45 ℃ after the sweating is finished, melting the residual crystals in the secondary melting crystallization kettle 4, pumping to the primary raw material storage tank 6 through a first material delivery pump 11, and returning to the primary melting crystallization process as a primary raw material.
Further, sweat in the third-stage raw material storage tank 9 is collected to a target amount and then is put into the third-stage melting crystallization kettle 5, the temperature is reduced to a third-stage crystallization temperature, after crystallization time is up, a sweat discharging valve is opened, the temperature is slowly raised to a target temperature for sweating and liquid discharging, the obtained third-stage sweat is collected into the tailing storage tank 10, after sweating is completed, the temperature is raised to 30-35 ℃ to melt residual crystals in the third-stage melting crystallization kettle 5, the residual crystals are pumped into the second-stage raw material storage tank 7 through a second-stage raw material delivery pump 12, and the residual crystals are returned to a second-stage melting crystallization.
Examples
Embodiments of the present invention will be described in detail below with reference to examples, but those skilled in the art will appreciate that the following examples are only illustrative of the present invention and should not be construed as limiting the scope of the present invention. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products commercially available.
The raw materials of the invention, such as 98 percent nitric acid, 98 percent sulfuric acid, o-dichlorobenzene and the like, are synthesized or purchased by traditional methods.
Example 1
(a) A nitration step: dropwise adding mixed acid (mass ratio of 98 wt% nitric acid to 98 wt% sulfuric acid is 1:3) into o-dichlorobenzene at 20 ℃, keeping the temperature at 60 ℃ to the end, removing an acid water layer by layers, adding 1500kg of 1% sodium bicarbonate solution at 55 ℃, removing the water layer by layers to obtain 624kg of nitration product with the purity of 92.59%, and placing the nitration product into a primary raw material storage tank 6.
(b) A first-stage melting crystallization step: sequentially putting the nitrated product prepared in the step (a) into three first-stage melting crystallization kettles 1, 2 and 3 at 55 ℃ by 200kg respectively, introducing a cold source medium 14, and then cooling to 26 ℃ for crystallization for 3.5 hours to obtain a first-stage crystallization product; opening a sweat discharging valve, introducing a heat source medium 13, melting and sweating the primary crystallization product again, controlling the heating rate at 3 ℃/h, stopping heating and preserving heat for 1 h when the temperature reaches 32 ℃, discharging the obtained primary sweat to a secondary raw material storage tank 7, after sweating, heating to 50 ℃, melting the residual crystals and putting the residual crystals to a finished product storage tank 8 to obtain the high-purity 3, 4-dichloronitrobenzene crystals, wherein the yield is 367kg, the yield is 61.17%, and the purity is 99.12%; the amount of the primary sweat was 231kg, and the purity was 87.53%.
(c) A secondary melting crystallization step: putting 200kg of secondary raw material (namely primary sweat) into a secondary melting crystallization kettle 4 at 45 ℃, introducing a cold source medium 14, cooling to 18 ℃, and crystallizing for 3.5 hours to obtain a secondary crystallization product; opening a sweat discharging valve, introducing a heat source medium 13, melting and sweating the secondary crystallization product again, controlling the temperature rising rate at 3 ℃/h, stopping temperature rising and keeping the temperature for 1 h when the temperature reaches 26 ℃, discharging the obtained secondary sweat to a tertiary raw material storage tank 9, after sweating is finished, heating to 40 ℃, melting the residual crystals, pumping the residual crystals to a primary raw material storage tank 6 by using a first material conveying pump 11, and using the residual crystals as a primary raw material for subsequent production, wherein the yield of the step is 113kg, the secondary yield is 56.50%, and the purity is 91.89%; the amount of secondary sweat was 87kg, and the purity was 77.58%.
(d) A third-stage melt crystallization step: putting 87kg of a third-level raw material (namely second-level sweat) into a third-level melting crystallization kettle 5 at the temperature of 30 ℃, introducing a cold source medium 14, cooling to 10 ℃, and crystallizing for 4 hours to obtain a third-level crystallization product; opening a sweat discharging valve, introducing a heat source medium 13, melting and sweating the tertiary crystallization product again, controlling the heating rate at 2.5 ℃/h, stopping heating and keeping the temperature for 1 h when the temperature reaches 17 ℃, discharging the obtained tertiary sweat to a tailing storage tank 10, heating to 30 ℃ after sweating, melting the residual crystals, pumping the residual crystals to a secondary raw material storage tank 7 by using a second raw material conveying pump 12, and using the residual crystals as a secondary raw material for subsequent production, wherein the yield of the step is 35kg, the tertiary yield is 40.70%, and the purity is 85.71%; the amount of tertiary sweat was 52kg, and the purity was 71.55%.
The overall yield was calculated as shown below:
wherein: r1In first order yield, R2For a second yield, R3The yield is three levels;
the total yield of this example was 82.47%, and the purity of the 3, 4-dichloronitrobenzene crystals was 99.12%.
Example 2
(a) A nitration step: dropwise adding mixed acid (mass ratio of 98 wt% nitric acid to 98 wt% sulfuric acid is 1:3) into o-dichlorobenzene at 20 ℃, keeping the temperature at 60 ℃ to the end, removing an acid water layer by layers, adding 1500kg of 1% sodium bicarbonate solution at 55 ℃, removing the water layer by layers to obtain 619kg of a nitration product with the purity of 92.38%, and placing the nitration product into a primary raw material storage tank 6.
(b) A first-stage melting crystallization step: sequentially putting the primary raw materials into 200kg of three primary melting crystallization kettles 1, 2 and 3 at 60 ℃, introducing a cold source medium 14, cooling to 27 ℃ and crystallizing for 4 hours to obtain primary crystallization products; opening a sweat discharging valve, introducing a heat source medium 13, melting and sweating the primary crystallization product again, controlling the heating rate at 2.5 ℃/h, stopping heating and preserving heat for 1 h when the temperature reaches 32 ℃, discharging the obtained primary sweat to a secondary raw material storage tank 7, after sweating, heating to 50 ℃, melting the residual crystals and placing the residual crystals to a finished product storage tank 8 to obtain the high-purity 3, 4-dichloronitrobenzene crystals, wherein the yield is 365kg, the yield is 60.85%, and the purity is 99.31%; the amount of the first-level sweat is 235kg, and the purity is 86.90%.
(c) A secondary melting crystallization step: putting 200kg of secondary raw materials into a secondary melting crystallization kettle 4 at 45 ℃, introducing a cold source medium 14, cooling to 19 ℃, and crystallizing for 4 hours to obtain a secondary crystallization product; opening a sweat discharging valve, introducing a heat source medium 13, melting and sweating the secondary crystallization product again, controlling the heating rate at 2.5 ℃/h, stopping heating and keeping the temperature for 1 h when the temperature reaches 26 ℃, discharging the obtained secondary sweat to a tertiary raw material storage tank 9, after sweating is finished, heating to 40 ℃, melting the residual crystals, pumping the residual crystals to a primary raw material storage tank 6 by using a first material conveying pump 11, and using the residual crystals as a primary raw material for subsequent production, wherein the yield of the step is 112kg, the secondary yield is 56.03%, and the purity is 92.22%; the amount of secondary sweat was 88kg, and the purity was 76.58%.
(d) A third-stage melt crystallization step: putting 88kg of tertiary raw materials into a tertiary melting crystallization kettle 5 at 30 ℃, introducing a cold source medium 14, cooling to 11 ℃, and crystallizing for 4.5 hours to obtain a tertiary crystallization product; opening a sweat discharging valve, introducing a heat source medium 13, melting and sweating the tertiary crystallization product, controlling the heating rate at 2 ℃/h, stopping heating and keeping the temperature for 1 h when the temperature reaches 17 ℃, discharging the obtained tertiary sweat to a tailing storage tank 10, after sweating is finished, heating to 30 ℃, melting the residual crystals, pumping the residual crystals to a secondary raw material storage tank 7 by using a second raw material conveying pump 12, and using the residual crystals as a secondary raw material for subsequent production, wherein the yield of the step is 35kg, the tertiary yield is 39.65%, and the purity is 86.08%; the amount of the third-level sweat is 53kg, and the purity is 71.34%.
The total yield of this example was 81.96% and the purity of the 3, 4-dichloronitrobenzene crystals was 99.31%.
Example 3
(a) A nitration step: dropwise adding mixed acid (mass ratio of 98 wt% nitric acid to 98 wt% sulfuric acid is 1:3) into o-dichlorobenzene at 20 ℃, keeping the temperature at 60 ℃ to the end, removing an acid water layer by layers, adding 1500kg of 1% sodium bicarbonate solution at 55 ℃, removing the water layer by layers to obtain 622kg of nitration product with the purity of 92.56%, and placing the nitration product into a primary raw material storage tank 6.
(b) A first-stage melting crystallization step: sequentially putting the primary raw materials into three primary melting crystallization kettles 1, 2 and 3 at 60 ℃ for 200kg respectively, introducing a cold source medium 14, and cooling to 28 ℃ for crystallization for 4.5 hours to obtain primary crystallization products; opening a sweat discharging valve, introducing a heat source medium 13, melting and sweating the primary crystallization product again, controlling the heating rate at 2 ℃/h, stopping heating and preserving heat for 1 h when the temperature reaches 33 ℃, discharging the obtained primary sweat to a secondary raw material storage tank 7, after sweating is finished, heating to 50 ℃, melting the residual crystals and putting the residual crystals to a finished product storage tank 8 to obtain the high-purity 3, 4-dichloronitrobenzene crystals, wherein the yield is 352kg, the yield is 58.69%, and the purity is 99.35%; the amount of the primary sweat is 248kg, and the purity is 86.79%.
(c) A secondary melting crystallization step: putting 200kg of secondary raw materials into a secondary melting crystallization kettle 4 at 45 ℃, introducing a cold source medium 14, cooling to 20 ℃, and crystallizing for 4.5 hours to obtain a secondary crystallization product; opening a sweat discharging valve, introducing a heat source medium 13, melting and sweating the secondary crystallization product again, controlling the temperature rising rate at 2 ℃/h, stopping temperature rising when the temperature rises to 27 ℃, keeping the temperature for 1 h, discharging the obtained secondary sweat to a tertiary raw material storage tank 9, after sweating, heating to 40 ℃, melting the residual crystals, pumping the residual crystals to a primary raw material storage tank 6 by using a first material conveying pump 11, and using the residual crystals as a primary raw material for subsequent production, wherein the yield of the step is 111kg, the secondary yield is 55.34%, and the purity is 92.55%; the amount of secondary sweat was 89kg, and the purity was 76.31%.
(d) A third-stage melt crystallization step: putting 89kg of tertiary raw materials into a tertiary melting crystallization kettle 5 at 30 ℃, introducing a cold source medium 14, cooling to 12 ℃, and crystallizing for 5 hours to obtain a tertiary crystallization product; opening a sweat discharging valve, introducing a heat source medium 13, melting and sweating the tertiary crystallization product again, controlling the heating rate at 1.5 ℃/h, stopping heating and keeping the temperature for 1 h when the temperature reaches 18 ℃, discharging the obtained tertiary sweat to a tailing storage tank 10, heating to 30 ℃ after sweating, melting the residual crystals, pumping the residual crystals to a secondary raw material storage tank 7 by using a second raw material conveying pump 12, and using the residual crystals as a secondary raw material for subsequent production, wherein the yield of the step is 32kg, the tertiary yield is 36.14%, and the purity is 87.32%; the amount of the third-level sweat is 57kg, and the purity is 72.11%.
The total yield of this example was 79.91%, and the purity of the 3, 4-dichloronitrobenzene crystals was 99.35%.
Example 4
(a) A nitration step: dropwise adding mixed acid (mass ratio of 98 wt% nitric acid to 98 wt% sulfuric acid is 1:3) into o-dichlorobenzene at 20 ℃, keeping the temperature at 60 ℃ to the end, removing an acid water layer by layers, adding 1500kg of 1% sodium bicarbonate solution at 55 ℃, removing the water layer by layers to obtain 622kg of nitration product with the purity of 92.49%, and placing the nitration product into a primary raw material storage tank 6.
(b) A first-stage melting crystallization step: sequentially putting the primary raw materials into three primary melting crystallization kettles 1, 2 and 3 at 60 ℃ for 200kg respectively, introducing a cold source medium 14, and cooling to 28 ℃ for crystallization for 3.5 hours to obtain primary crystallization products; opening a sweat discharging valve, introducing a heat source medium 13, melting and sweating the primary crystallization product again, controlling the heating rate at 2 ℃/h, stopping heating and preserving heat for 1 h when the temperature reaches 33 ℃, discharging the obtained primary sweat to a secondary raw material storage tank 7, after sweating is finished, heating to 50 ℃, melting the residual crystals and putting the residual crystals to a finished product storage tank 8 to obtain the high-purity 3, 4-dichloronitrobenzene crystals, wherein the yield is 356kg, the yield is 59.37%, and the purity is 99.27%; the amount of the primary sweat is 244kg, and the purity is 87.01%.
(c) A secondary melting crystallization step: putting 200kg of secondary raw materials into a secondary melting crystallization kettle 4 at 45 ℃, introducing a cold source medium 14, cooling to 20 ℃, and crystallizing for 3.5 hours to obtain a secondary crystallization product; opening a sweat discharging valve, introducing a heat source medium 13, melting and sweating the secondary crystallization product again, controlling the temperature rising rate at 2 ℃/h, stopping temperature rising when the temperature rises to 27 ℃, keeping the temperature for 1 h, discharging the obtained secondary sweat to a tertiary raw material storage tank 9, after sweating is finished, heating to 40 ℃, melting the residual crystals, pumping the residual crystals to a primary raw material storage tank 6 by using a first material conveying pump 11, and using the residual crystals as a primary raw material for subsequent production, wherein the yield of the step is 112kg, the secondary yield is 55.78%, and the purity is 92.39%; the amount of secondary sweat was 88kg, and the purity was 76.91%.
(d) A third-stage melt crystallization step: putting 88kg of tertiary raw materials into a tertiary melt crystallization kettle 5 at 30 ℃, introducing a cold source medium 14, cooling to 12 ℃, and crystallizing for 4 hours to obtain a tertiary crystallization product; opening a sweat discharging valve, introducing a heat source medium 13, melting and sweating the tertiary crystallization product again, controlling the heating rate at 1.5 ℃/h, stopping heating and keeping the temperature for 1 h when the temperature reaches 18 ℃, discharging the obtained tertiary sweat to a tailing storage tank 10, heating to 30 ℃ after sweating, melting the residual crystals, pumping the residual crystals to a secondary raw material storage tank 7 by using a second raw material conveying pump 12, and using the residual crystals as a secondary raw material for subsequent production, wherein the yield of the step is 35kg, the tertiary yield is 39.91%, and the purity is 86.37%; the amount of tertiary sweat is 53kg, and the purity is 71.69%.
The total yield of this example was 80.96%, and the purity of the 3, 4-dichloronitrobenzene crystals was 99.27%.
Example 5
(a) A nitration step: dropwise adding mixed acid (mass ratio of 98 wt% nitric acid to 98 wt% sulfuric acid is 1:3) into o-dichlorobenzene at 20 ℃, keeping the temperature at 60 ℃ to the end, removing an acid water layer by layers, adding 1500kg of 1% sodium bicarbonate solution at 55 ℃, removing the water layer by layers to obtain 627kg of nitration product with the purity of 92.12%, and placing the nitration product into a primary raw material storage tank 6.
(b) A first-stage melting crystallization step: sequentially putting the primary raw materials into 200kg of three primary melting crystallization kettles 1, 2 and 3 at 60 ℃, introducing a cold source medium 14, cooling to 27 ℃ and crystallizing for 4 hours to obtain primary crystallization products; opening a sweat discharging valve, introducing a heat source medium 13, melting and sweating the primary crystallization product again, controlling the heating rate at 2 ℃/h, stopping heating and preserving heat for 1 h when the temperature reaches 33 ℃, discharging the obtained primary sweat to a secondary raw material storage tank 7, after sweating is finished, heating to 50 ℃, melting the residual crystals and putting the residual crystals to a finished product storage tank 8 to obtain the high-purity 3, 4-dichloronitrobenzene crystals, wherein the yield is 359kg, the yield is 59.84%, and the purity is 99.31%; the amount of the primary sweat is 241kg, and the purity is 86.65%.
(c) A secondary melting crystallization step: putting 200kg of secondary raw materials into a secondary melting crystallization kettle 4 at 45 ℃, introducing a cold source medium 14, cooling to 19 ℃, and crystallizing for 4 hours to obtain a secondary crystallization product; opening a sweat discharging valve, introducing a heat source medium 13, melting and sweating the secondary crystallization product again, controlling the temperature rising rate at 2 ℃/h, stopping temperature rising until the temperature reaches 26 ℃, keeping the temperature for 1 h, discharging the obtained secondary sweat to a tertiary raw material storage tank 9, after sweating, heating to 40 ℃, melting the residual crystals, pumping the residual crystals to a primary raw material storage tank 6 by using a first material conveying pump 11, and using the residual crystals as a primary raw material for subsequent production, wherein the yield of the step is 112kg, the secondary yield is 55.88%, and the purity is 92.25%; the amount of the second-level sweat is 88kg, and the purity is 76.43%.
(d) A third-stage melt crystallization step: putting 88kg of tertiary raw materials into a tertiary melting crystallization kettle 5 at 30 ℃, introducing a cold source medium 14, cooling to 11 ℃, and crystallizing for 4.5 hours to obtain a tertiary crystallization product; opening a sweat discharging valve, introducing a heat source medium 13, melting and sweating the tertiary crystallization product again, controlling the heating rate at 1.5 ℃/h, stopping heating and keeping the temperature for 1 h when the temperature reaches 17 ℃, discharging the obtained tertiary sweat to a tailing storage tank 10, heating to 30 ℃ after sweating, melting the residual crystals, pumping the residual crystals to a secondary raw material storage tank 7 by using a second raw material conveying pump 12, and using the residual crystals as a secondary raw material for subsequent production, wherein the yield of the step is 35kg, the tertiary yield is 39.73%, and the purity is 86.31%; the amount of tertiary sweat is 53kg, and the purity is 71.53%.
The total yield of this example was 81.28%, and the purity of the 3, 4-dichloronitrobenzene crystals was 99.31%.
It should be noted that, although the technical solutions of the present invention are described by specific examples, those skilled in the art can understand that the present invention should not be limited thereto.
Having described embodiments of the present invention, the foregoing description is intended to be exemplary, not exhaustive, and not limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen in order to best explain the principles of the embodiments, the practical application, or improvements made to the technology in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein.
Claims (13)
1. A method for purifying 3, 4-dichloronitrobenzene is characterized by comprising the following steps:
a nitration step: reacting o-dichlorobenzene with mixed acid to obtain a nitration product;
a first-stage melting crystallization step: melting the nitration product, and then cooling and crystallizing to obtain a primary crystallization product; and the number of the first and second electrodes,
and melting and sweating the primary crystallization product again to obtain primary sweat and 3, 4-dichloronitrobenzene crystals.
2. The purification method of claim 1, further comprising a secondary melt crystallization step; the secondary melting crystallization step comprises melting the primary sweat, cooling and crystallizing to obtain a secondary crystallization product; and the number of the first and second electrodes,
melting and sweating the secondary crystallization product again to obtain secondary sweat and primary raw material crystals; wherein
The primary raw material crystals can be mixed with the nitration product and subjected to the primary melt crystallization.
3. The purification method of claim 2, further comprising a three-stage melt crystallization step; the third-stage melting crystallization step comprises the steps of melting the second-stage sweat, cooling and crystallizing to obtain a third-stage crystallization product; and the number of the first and second electrodes,
melting and sweating the tertiary crystallization product again to obtain tertiary sweat and secondary raw material crystals; wherein
The secondary raw material crystals can be mixed with the primary sweat and subjected to the secondary melt crystallization.
4. The purification method according to any one of claims 1 to 3, wherein in the nitration step, the mixed acid is dropwise added into the o-dichlorobenzene at the temperature of 20-30 ℃, then the heat preservation reaction is carried out at the temperature of 55-60 ℃, and the nitration product is obtained after the post-treatment.
5. The purification method according to claim 4, wherein the post-treatment comprises a step of neutralization treatment with an alkaline solution; preferably, the concentration of an alkaline agent in the alkaline solution is 1-1.5 wt%, the temperature of the neutralization treatment is 50-60 ℃, and the usage amount of the alkaline solution is 2-3 times of the mass of the nitration product.
6. The purification method according to any one of claims 1 to 5, wherein in the primary melt crystallization step, the melting temperature is 55 to 60 ℃, the crystallization temperature is 25 to 30 ℃, and the crystallization time is 3.5 to 4.5 hours;
the temperature for remelting and sweating is 30-35 ℃, and the time for remelting and sweating is 0.5-1.5 hours;
preferably, the first-stage crystallization product is melted again for sweating by means of temperature rise, and more preferably, the temperature rise rate is 1-5 ℃/hour.
7. The purification method according to claim 2 or 3, wherein in the secondary melting and crystallization step, the melting temperature is 45-55 ℃, the crystallization temperature is 17-22 ℃, and the crystallization time is 3.5-4.5 hours;
the temperature for remelting and sweating is 24-29 ℃, and the time for remelting and sweating is 0.5-1.5 hours;
preferably, the secondary crystallization product is melted again for sweating by means of temperature rise, and more preferably, the temperature rise rate is 1-5 ℃/hour.
8. The purification method according to claim 3, wherein in the three-stage melting and crystallization step, the melting temperature is 30-35 ℃, the crystallization temperature is 9-14 ℃, and the crystallization time is 4.0-5.0 hours;
the temperature for remelting and sweating is 15-20 ℃, and the time for remelting and sweating is 0.5-1.5 hours;
preferably, the tertiary crystallization product is melted again for sweating by means of temperature rise, and more preferably, the temperature rise rate is 0.5-4 ℃/hour.
9. A purification apparatus for carrying out the purification method according to any one of claims 1 to 6, wherein the purification apparatus comprises at least one melt crystallization vessel.
10. The purification device of claim 9, wherein the purification device comprises a primary melt crystallization kettle, a secondary melt crystallization kettle and a tertiary melt crystallization kettle which are connected in sequence; wherein the content of the first and second substances,
the discharge port of the second-stage melting crystallization kettle is connected with the feed inlet of the first-stage melting crystallization kettle, and the discharge port of the third-stage melting crystallization kettle is connected with the feed inlet of the second-stage melting crystallization kettle.
11. The purifying device of claim 9 or 10, wherein a plurality of sets of tube arrays are arranged inside the melt crystallization kettle;
preferably, the diameter of the tube array is 40-50 mm, and the distance between the tube array and the tube array is 20-30 mm.
12. The purifying apparatus of claim 11, wherein a heat source medium and a heat sink medium are inserted into the outer jackets of the tubes.
13. The refining apparatus of claim 9 or 10, further comprising at least one storage tank.
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| CN115611745A (en) * | 2022-09-26 | 2023-01-17 | 浙江闰土股份有限公司 | Method for continuously producing 3, 4-dichloronitrobenzene |
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Application publication date: 20210416 |