CN117756638A - Method and system for continuously purifying 2, 4-dinitrochlorobenzene - Google Patents
Method and system for continuously purifying 2, 4-dinitrochlorobenzene Download PDFInfo
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- CN117756638A CN117756638A CN202311670425.9A CN202311670425A CN117756638A CN 117756638 A CN117756638 A CN 117756638A CN 202311670425 A CN202311670425 A CN 202311670425A CN 117756638 A CN117756638 A CN 117756638A
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- dinitrochlorobenzene
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- VYZAHLCBVHPDDF-UHFFFAOYSA-N Dinitrochlorobenzene Chemical compound [O-][N+](=O)C1=CC=C(Cl)C([N+]([O-])=O)=C1 VYZAHLCBVHPDDF-UHFFFAOYSA-N 0.000 title claims abstract description 78
- 238000000034 method Methods 0.000 title claims abstract description 35
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims abstract description 174
- 238000000605 extraction Methods 0.000 claims abstract description 88
- 238000002425 crystallisation Methods 0.000 claims abstract description 84
- 230000008025 crystallization Effects 0.000 claims abstract description 84
- 238000004090 dissolution Methods 0.000 claims abstract description 80
- 239000000706 filtrate Substances 0.000 claims abstract description 67
- 239000013078 crystal Substances 0.000 claims abstract description 60
- 239000000047 product Substances 0.000 claims abstract description 49
- 238000000926 separation method Methods 0.000 claims abstract description 17
- 238000002844 melting Methods 0.000 claims abstract description 11
- 230000008018 melting Effects 0.000 claims abstract description 11
- 238000001035 drying Methods 0.000 claims abstract description 9
- 239000000155 melt Substances 0.000 claims abstract description 4
- 238000000746 purification Methods 0.000 claims description 21
- 239000002994 raw material Substances 0.000 claims description 21
- 238000010438 heat treatment Methods 0.000 claims description 12
- 238000004519 manufacturing process Methods 0.000 claims description 6
- 239000000463 material Substances 0.000 claims description 3
- BPPMIQPXQVIZNJ-UHFFFAOYSA-N 2-chloro-1,3-dinitrobenzene Chemical compound [O-][N+](=O)C1=CC=CC([N+]([O-])=O)=C1Cl BPPMIQPXQVIZNJ-UHFFFAOYSA-N 0.000 description 10
- 238000001914 filtration Methods 0.000 description 9
- 239000012535 impurity Substances 0.000 description 5
- 239000000543 intermediate Substances 0.000 description 5
- 238000001816 cooling Methods 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- 230000035900 sweating Effects 0.000 description 4
- 230000000694 effects Effects 0.000 description 3
- 230000014759 maintenance of location Effects 0.000 description 3
- PGYZAKRTYUHXRA-UHFFFAOYSA-N 2,10-dinitro-12h-[1,4]benzothiazino[3,2-b]phenothiazin-3-one Chemical compound S1C2=CC(=O)C([N+]([O-])=O)=CC2=NC2=C1C=C1SC3=CC=C([N+](=O)[O-])C=C3NC1=C2 PGYZAKRTYUHXRA-UHFFFAOYSA-N 0.000 description 2
- 238000010923 batch production Methods 0.000 description 2
- 239000006227 byproduct Substances 0.000 description 2
- MVPPADPHJFYWMZ-UHFFFAOYSA-N chlorobenzene Chemical compound ClC1=CC=CC=C1 MVPPADPHJFYWMZ-UHFFFAOYSA-N 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 239000003814 drug Substances 0.000 description 2
- 229940079593 drug Drugs 0.000 description 2
- 239000000575 pesticide Substances 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- BFCFYVKQTRLZHA-UHFFFAOYSA-N 1-chloro-2-nitrobenzene Chemical compound [O-][N+](=O)C1=CC=CC=C1Cl BFCFYVKQTRLZHA-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 238000010924 continuous production Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000000975 dye Substances 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 239000002360 explosive Substances 0.000 description 1
- 239000012847 fine chemical Substances 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000012452 mother liquor Substances 0.000 description 1
- 239000010413 mother solution Substances 0.000 description 1
- 238000006396 nitration reaction Methods 0.000 description 1
- 150000002828 nitro derivatives Chemical class 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 210000004243 sweat Anatomy 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
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- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
The invention discloses a method and a system for continuously purifying 2, 4-dinitrochlorobenzene, which takes methanol as an extractant and comprises the following steps: continuously adding the melt crude 2, 4-dinitrochlorobenzene and filtrate separated by secondary extraction crystallization into a primary dissolution kettle, controlling the temperature to completely dissolve the crude, adding the crude into a primary extraction crystallization unit for primary extraction crystallization separation, and using the filtrate separated by primary extraction crystallization for recovering methanol in a rectifying tower; continuously melting the crystals separated by the primary extraction crystallization, continuously adding the filtrate separated by the tertiary extraction crystallization into a secondary dissolution kettle, controlling the temperature to completely dissolve the crystals, and adding the filtrate into a secondary extraction crystallization unit to perform secondary extraction crystallization separation; continuously melting the crystals separated by the secondary extraction crystallization, continuously adding the crystals and the methanol recovered by the rectifying tower into a three-time dissolution kettle, controlling the temperature to completely dissolve the crystals, and adding the crystals into a three-time extraction crystallization unit for three-time extraction crystallization separation; and drying the crystals separated by three times of extraction crystallization to obtain the 2, 4-dinitrochlorobenzene product.
Description
Technical Field
The invention relates to the technical field of 2, 4-dinitrochlorobenzene purification, in particular to a method and a system for continuously purifying 2, 4-dinitrochlorobenzene.
Background
The 2, 4-dinitrochlorobenzene is an important fine chemical intermediate, is widely applied to the fields of dyes, pesticides, explosives, chemical intermediates, medicines, chemical assistants and the like, and has good development prospect. The standard of the China chemical industry (HG/T2553-2018) prescribes that the products can be classified into high-grade products, first-grade products and qualified products according to the crystallization point and the purity of the products, wherein the purity of the high-grade products is more than or equal to 99.80 percent, the purity of the first-grade products is more than or equal to 99.00 percent, and the purity of the qualified products is more than or equal to 95.00 percent.
At present, the common synthetic mode of 2, 4-dinitrochlorobenzene is that chlorobenzene or nitrochlorobenzene is subjected to nitration reaction, by-product isomers (such as 2, 6-dinitrochlorobenzene and the like) are generated in the reaction process, the chemical properties of the by-product isomers are very similar, particularly the boiling points are closer, so that the separation effect is difficult to achieve by the existing separation technology such as rectification and the like, and the product quality is poor. The nitro compound is easy to decompose and possibly explode at high temperature, so that great potential safety hazards exist, the existing separation process is mostly a batch process, and a continuous separation method is seldom adopted.
The Chinese patent application publication No. CN104045563A discloses a method for producing high-purity 2, 4-dinitrochlorobenzene, but the method does not disclose the purity and yield of the product, does not separate isomers of the target product, and cannot realize serialization.
The chinese patent application publication No. CN113582850a discloses a method for purifying 2, 4-dinitrochlorobenzene, wherein 2, 4-dinitrochlorobenzene crystals with purity of more than 99.5% are obtained through the processes of cooling crystallization and heating sweating, but the purity of the method is much lower than that of the superior product, and the method is a batch process, and the time is long, so that the continuity is not realized.
The Chinese patent application publication No. CN113651699A discloses a method for preparing high-purity 2, 4-dinitrochlorobenzene by layered melt crystallization, and the superior product of the 2, 4-dinitrochlorobenzene with the purity of more than 99.8% is obtained through the processes of cooling crystallization and heating sweating, but the serialization cannot be realized.
The prior art method has the defects of poor product quality and low quality, can not meet the requirements of products such as novel medicines and pesticides, can not realize continuous production, and has low production efficiency. In view of the increasing requirements for the purification of 2, 4-dinitrochlorobenzene in the future, it is of great importance to find a novel, high-quality and efficient continuous purification method.
Disclosure of Invention
Aiming at the technical problems and the defects existing in the field, the invention provides a method and a system for continuously purifying 2, 4-dinitrochlorobenzene, which can efficiently separate impurities such as 2, 6-dinitrochlorobenzene and the like from the 2, 4-dinitrochlorobenzene, effectively separate dinitrochlorobenzene isomers, ensure the quality and the yield of 2, 4-dinitrochlorobenzene products and shorten the purification time.
A method for continuously purifying 2, 4-dinitrochlorobenzene by using methanol as an extractant comprises the following steps:
continuously adding the melt crude 2, 4-dinitrochlorobenzene and the filtrate separated by secondary extraction crystallization into a primary dissolution kettle, controlling the temperature to completely dissolve the crude 2, 4-dinitrochlorobenzene, adding the solution into a primary extraction crystallization unit, performing primary extraction crystallization separation, and using the filtrate separated by primary extraction crystallization to recover methanol in a rectifying tower;
continuously melting the crystals separated by the primary extraction crystallization, continuously adding the filtrate separated by the tertiary extraction crystallization into a secondary dissolution kettle, controlling the temperature to completely dissolve the crystals, and adding the filtrate into a secondary extraction crystallization unit to perform secondary extraction crystallization separation;
continuously melting the crystals separated by the secondary extraction crystallization, continuously adding the crystals and the methanol recovered by the rectifying tower into a three-time dissolution kettle, controlling the temperature to completely dissolve the crystals, and adding the crystals into a three-time extraction crystallization unit to perform three-time extraction crystallization separation;
and drying the crystals separated by three times of extraction crystallization to obtain the 2, 4-dinitrochlorobenzene product.
The primary extraction crystallization unit, the secondary extraction crystallization unit and the tertiary extraction crystallization unit can respectively and independently comprise 1-3 crystallizers.
The rectifying column tailing can be used for producing sulfur black.
The temperature of the primary dissolution kettle, the secondary dissolution kettle and the tertiary dissolution kettle can be independently controlled at 50-65 ℃, preferably 55-60 ℃.
The content of 2, 4-dinitrochlorobenzene in the crude 2, 4-dinitrochlorobenzene may be from 85% to 95% by weight, preferably from 87% to 92% by weight.
The mass ratio of the molten crude 2, 4-dinitrochlorobenzene or crystal to filtrate or methanol added into the primary dissolution kettle, the secondary dissolution kettle or the tertiary dissolution kettle can be respectively and independently 1:1.5-2.5, and preferably respectively and independently 1:1.8-2.3.
The crystallization temperatures of the primary extraction crystallization unit, the secondary extraction crystallization unit and the tertiary extraction crystallization unit can be independently controlled at-5-15 ℃, preferably at 0-10 ℃, and the material residence time can be independently controlled at 2-6 h, preferably at 1-5 h.
The temperature of the reboiler of the rectifying tower can be controlled between 65 and 85 ℃, preferably between 70 and 78 ℃, and the temperature of the top of the rectifying tower can be controlled between 60 and 75 ℃, preferably between 65 and 70 ℃.
A system for continuously purifying 2, 4-dinitrochlorobenzene comprises a primary dissolution kettle, a secondary dissolution kettle and a tertiary dissolution kettle;
the primary dissolution kettle, the primary extraction crystallization unit and the primary filter are sequentially connected, and the primary filter is connected with a primary filtrate tank for collecting filtrate and a primary product buffer tank for collecting and heating molten crystals;
the secondary dissolution kettle, the secondary extraction crystallization unit and the secondary filter are sequentially connected, and the secondary filter is connected with a secondary filtrate tank for collecting filtrate and a secondary product buffer tank for collecting and heating molten crystals;
the third dissolution kettle, the third extraction crystallization unit and the third filter are sequentially connected, and the third filter is connected with a third filtrate tank for collecting filtrate and a third product tank for collecting and drying crystals;
the primary filtrate tank, the rectifying tower and the third dissolution kettle are connected in sequence; the third dissolution kettle is also connected with a secondary product buffer tank;
the secondary dissolution kettle is connected with the tertiary filtrate tank and the primary product buffer tank;
the primary dissolution kettle is connected with the secondary filtrate tank.
A methanol raw material tank can be arranged between the rectifying tower and the third dissolution kettle. The methanol raw material tank stores high-purity methanol raw material, can receive methanol recovered by rectification of the rectifying tower, and provides methanol for the third dissolution kettle as an extractant. During long-term operation, the methanol raw material tank can be properly supplemented with methanol raw material.
The rectifying tower can also be connected with a tail trough.
The system for continuously purifying 2, 4-dinitrochlorobenzene can be used for executing the method for continuously purifying 2, 4-dinitrochlorobenzene.
Compared with the prior art, the invention has the beneficial effects that:
1. the invention provides a method and a system for continuously purifying 2, 4-dinitrochlorobenzene, which ensure safer process and lower production cost.
2. The crude 2, 4-dinitrochlorobenzene and the crystals in the intermediate process are molten, methanol is used for extracting impurities such as 2, 6-dinitrochlorobenzene and the like in the crude and intermediate crystals, and the use amount of the extractant methanol can be reduced in the molten state of the crude and intermediate crystals.
3. The invention adopts methanol as the extractant, has high selectivity to 2, 6-dinitrochlorobenzene, good extraction effect, easy separation of methanol, low recovery cost, repeated use, no need of tail gas treatment and environmental protection.
4. The invention has good purification effect, the purity of the 2, 4-dinitrochlorobenzene product after purification can exceed 99.9 percent, the quality product is achieved, and the corresponding yield can also exceed 80 percent.
Drawings
FIG. 1 is a schematic flow chart of a process for continuously purifying 2, 4-dinitrochlorobenzene according to the invention.
FIG. 2 is a schematic diagram of a system for continuously purifying 2, 4-dinitrochlorobenzene according to the present invention.
Detailed Description
The invention will be further elucidated with reference to the drawings and to specific embodiments. It is to be understood that these examples are illustrative of the present invention and are not intended to limit the scope of the present invention.
The methods of operation, under which specific conditions are not noted in the examples below, are generally in accordance with conventional conditions, or in accordance with the conditions recommended by the manufacturer.
The flow of the method for continuously purifying 2, 4-dinitrochlorobenzene is shown in figure 1, and the structure of a system for continuously purifying 2, 4-dinitrochlorobenzene which is matched with the flow is shown in figure 2.
Referring to FIG. 1, a method for continuously purifying 2, 4-dinitrochlorobenzene by using methanol as an extractant comprises:
continuously adding the melt crude 2, 4-dinitrochlorobenzene and the filtrate separated by secondary extraction crystallization into a primary dissolution kettle, controlling the temperature to completely dissolve the crude 2, 4-dinitrochlorobenzene, adding the solution into a primary extraction crystallization unit, performing primary extraction crystallization separation, using the filtrate separated by primary extraction crystallization for recovering methanol in a rectifying tower, caching the methanol recovered in the rectifying tower in a methanol raw material tank, storing the rectifying tower tailing in a tailing tank, and using the tailing for producing sulfur black;
continuously melting the crystals separated by the primary extraction crystallization, continuously adding the filtrate separated by the tertiary extraction crystallization into a secondary dissolution kettle, controlling the temperature to completely dissolve the crystals, and adding the filtrate into a secondary extraction crystallization unit to perform secondary extraction crystallization separation;
continuously melting the crystals separated by the secondary extraction crystallization, continuously adding the crystals and the methanol recovered by the rectifying tower into a three-time dissolution kettle, controlling the temperature to completely dissolve the crystals, and adding the crystals into a three-time extraction crystallization unit to perform three-time extraction crystallization separation;
and drying the crystals separated by three times of extraction crystallization to obtain the 2, 4-dinitrochlorobenzene product.
Referring to FIG. 2, a system for continuously purifying 2, 4-dinitrochlorobenzene comprises a primary dissolution kettle 1, a secondary dissolution kettle 8 and a tertiary dissolution kettle 15.
The primary dissolution kettle 1, the primary extraction crystallizer 2 and the primary filter 3 are sequentially connected, and the primary filter 3 is connected with a primary filtrate tank 4 for collecting filtrate and a primary product buffer tank 5 for collecting and heating molten crystals. The primary filtrate tank 4, the first metering pump 6, the rectifying tower 21, the methanol raw material tank 22, the sixth metering pump 24 and the third dissolution kettle 15 are connected in sequence. The rectifying tower 21 is also connected with a tail trough 23. The primary product buffer tank 5 is connected with a secondary dissolution kettle 8 through a second metering pump 7.
The secondary dissolution kettle 8, the secondary extraction crystallizer 9 and the secondary filter 10 are sequentially connected, and the secondary filter 10 is connected with a secondary filtrate tank 11 for collecting filtrate and a secondary product buffer tank 12 for collecting and heating molten crystals. The secondary filtrate tank 11 is connected with the primary dissolution kettle 1 through a third metering pump 13. The secondary product buffer tank 12 is connected with a tertiary dissolution kettle 15 through a fourth metering pump 14.
The third dissolution kettle 15, the third extraction crystallizer 16 and the third filter 17 are connected in sequence, and the third filter 17 is connected with a third filtrate tank 18 for collecting filtrate and a third product tank 19 for collecting and drying crystals. The third filtrate tank 18 is connected with the secondary dissolution kettle 8 through a fifth metering pump 20.
The primary extraction crystallizer 2, the secondary extraction crystallizer 9 and the tertiary extraction crystallizer 16 can all adopt hot water to control the temperature.
Example 1
In this example, the raw material of the molten crude 2, 4-dinitrochlorobenzene (mass fraction 88% and the remainder of impurities mainly 2, 6-dinitrochlorobenzene, etc.) was used. A process for the continuous purification of 2, 4-dinitrochlorobenzene as shown in FIG. 1 is used, as is a system for the continuous purification of 2, 4-dinitrochlorobenzene as shown in FIG. 2.
(1) The feeding amount of the melted crude 2, 4-dinitrochlorobenzene is 520kg/h, the feeding amount of methanol filtrate separated by secondary extraction crystallization is 936kg/h, the mixture is continuously added into a primary dissolution kettle 1, the temperature is controlled to 55 ℃, the primary extraction crystallizer 2 is added after dissolution, the temperature is controlled to 5 ℃, crystallization filtration is carried out, the filtrate is used for rectifying and recovering methanol, the temperature of a reboiler at the bottom of a rectifying tower is 75 ℃, the temperature of a condenser at the top of the rectifying tower is 68 ℃, and crystals are melted.
(2) The feeding amount of the melted crystal product in the step (1) is 520kg/h, the feeding amount of the methanol filtrate separated by three times of extraction crystallization is 936kg/h, the methanol filtrate is continuously added into a secondary dissolution kettle 8, the temperature is controlled to 55 ℃, the dissolved methanol filtrate is added into a secondary extraction crystallizer 9, the temperature is controlled to 5 ℃, the crystallization filtration is carried out, and the filtrate is used for the primary dissolution kettle 1 and the crystal melting.
(3) The feeding amount of the molten crystal product in the step (2) is 520kg/h, the methanol recovered by rectification is stored in a methanol raw material tank 22, 936kg/h of the feeding amount of the methanol provided by the methanol raw material tank 22 to a tertiary dissolution kettle 15 is continuously added into the tertiary dissolution kettle 15, the temperature is controlled to 55 ℃, the tertiary extraction crystallizer 16 is added after dissolution, the temperature is controlled to 5 ℃, the crystallization filtration is carried out, the filtrate is used for a secondary dissolution kettle 8, and the crystal is dried, thus obtaining the 2, 4-dinitrochlorobenzene product.
The continuous purification is carried out for 32 hours, the retention time of each extraction crystallizer is 3 hours, the product quality and the corresponding raw material consumption are analyzed, the 2, 4-dinitrochlorobenzene content is 99.86wt%, the yield is 77wt%, and no tail gas is generated.
Example 2
In this example, the raw material of the molten crude 2, 4-dinitrochlorobenzene (mass fraction 90%, the remainder of impurities mainly being 2, 6-dinitrochlorobenzene, etc.) was used. A process for the continuous purification of 2, 4-dinitrochlorobenzene as shown in FIG. 1 is used, as is a system for the continuous purification of 2, 4-dinitrochlorobenzene as shown in FIG. 2.
(1) The raw 2, 4-dinitrochlorobenzene is melted, the feeding amount is 620kg/h, the methanol filtrate is 1240kg/h, which is separated by secondary extraction crystallization, and is continuously added into a primary dissolution kettle 1, the temperature is controlled to 55 ℃, a primary extraction crystallizer 2 is added after dissolution, the temperature is controlled to 5 ℃, crystallization filtration is carried out, the filtrate is used for rectifying and recovering methanol, the temperature of a reboiler at the bottom of a rectifying tower is 75 ℃, the temperature of a condenser at the top of the rectifying tower is 68 ℃, and the crystals are melted.
(2) The feeding amount of the melted crystal product in the step (1) is 620kg/h, the feeding amount of the methanol filtrate separated by three times of extraction crystallization is 1240kg/h, the methanol filtrate is continuously added into a secondary dissolution kettle 8, the temperature is controlled to 55 ℃, the dissolved methanol filtrate is added into a secondary extraction crystallizer 9, the temperature is controlled to 5 ℃, the crystallization filtration is carried out, and the filtrate is used for the primary dissolution kettle 1 and the crystal melting.
(3) And (3) feeding 620kg/h of molten crystal products in the step (2), storing methanol recovered by rectification in a methanol raw material tank 22, continuously adding 1240kg/h of methanol fed into a tertiary dissolution kettle 15 by the methanol raw material tank 22, controlling the temperature to 55 ℃, adding a tertiary extraction crystallizer 16 after dissolution, controlling the temperature to 5 ℃, crystallizing and filtering, using filtrate in a secondary dissolution kettle 8, and drying crystals to obtain the 2, 4-dinitrochlorobenzene product.
The continuous purification is carried out for 32 hours, the retention time of each extraction crystallizer is 3 hours, the product quality and the corresponding raw material consumption are analyzed, the 2, 4-dinitrochlorobenzene content is 99.90wt%, the yield is 80wt%, and no tail gas is generated.
Example 3
In this example, the raw material of the molten crude 2, 4-dinitrochlorobenzene (mass fraction 92%, the remainder of impurities mainly being 2, 6-dinitrochlorobenzene, etc.) was used. A process for the continuous purification of 2, 4-dinitrochlorobenzene as shown in FIG. 1 is used, as is a system for the continuous purification of 2, 4-dinitrochlorobenzene as shown in FIG. 2.
(1) The feeding amount of the melted crude 2, 4-dinitrochlorobenzene is 580kg/h, the feeding amount of the methanol filtrate separated by secondary extraction crystallization is 1334kg/h, the methanol filtrate is continuously added into a primary dissolution kettle 1, the temperature is controlled to 55 ℃, the primary extraction crystallizer 2 is added after dissolution, the temperature is controlled to 5 ℃, the crystallization filtration is carried out, the filtrate is used for rectifying and recovering methanol, the temperature of a reboiler at the bottom of a rectifying tower is 75 ℃, the temperature of a condenser at the top of the rectifying tower is 68 ℃, and the crystals are melted.
(2) The feeding amount of the molten crystal product in the step (1) is 580kg/h, the feeding amount of the methanol filtrate separated by three times of extraction crystallization is 1334kg/h, the methanol filtrate is continuously added into a secondary dissolution kettle 8, the temperature is controlled to 55 ℃, the dissolved methanol filtrate is added into a secondary extraction crystallizer 9, the temperature is controlled to 5 ℃, the crystallization filtration is carried out, and the filtrate is used for the primary dissolution kettle 1 and the crystal melting.
(3) And (3) feeding 580kg/h of molten crystal products in the step (2), storing methanol recovered by rectification in a methanol raw material tank 22, continuously adding 1334kg/h of methanol fed into a tertiary dissolution kettle 15 by the methanol raw material tank 22, controlling the temperature to 55 ℃, adding a tertiary extraction crystallizer 16 after dissolution, controlling the temperature to 5 ℃, crystallizing and filtering, using filtrate in a secondary dissolution kettle 8, and drying crystals to obtain the 2, 4-dinitrochlorobenzene product.
The continuous purification is carried out for 32 hours, the retention time of each extraction crystallizer is 3 hours, the product quality and the corresponding raw material consumption are analyzed, the 2, 4-dinitrochlorobenzene content is 99.92wt%, the yield is 83wt%, and no tail gas is generated.
Comparative example 1
Delivering the mixed mother liquor of the 2, 4-dinitrochlorobenzene (the content is 90 wt%) and the 2, 6-dinitrochlorobenzene (the content is 10 wt%) into a crystallizer, and cooling to 15 ℃ at the cooling rate of 0.15 ℃/min; gradually heating the cooled mixed mother solution to enable the crystal to sweat, wherein the heating rate is 0.06 ℃/min, the final temperature is 51 ℃, and the total heating and sweating time is controlled to be 10 hours; in the heating and sweating process, firstly collecting mixed low oil, wherein the mixed low oil contains 10% of 2, 6-dinitrochlorobenzene by volume fraction; and collecting mixed high oil, wherein the mixed high oil contains 2, 6-dinitrochlorobenzene with the volume fraction of 10%, and finally 2, 4-dinitrochlorobenzene crystals with the purity of 99.5% are obtained, and the crystallization yield is 82.0%.
The invention can accurately control the material feeding amount, improves the capability of purifying 2, 4-dinitrochlorobenzene, shortens the purification time, simultaneously circularly utilizes methanol, reduces the raw material consumption, reduces the purification cost, and has no production tail gas production, thereby being environment-friendly.
Further, it will be understood that various changes and modifications may be made by those skilled in the art after reading the foregoing description of the invention, and such equivalents are intended to fall within the scope of the claims appended hereto.
Claims (10)
1. A method for continuously purifying 2, 4-dinitrochlorobenzene is characterized by taking methanol as an extractant and comprising the following steps:
continuously adding the melt crude 2, 4-dinitrochlorobenzene and the filtrate separated by secondary extraction crystallization into a primary dissolution kettle, controlling the temperature to completely dissolve the crude 2, 4-dinitrochlorobenzene, adding the solution into a primary extraction crystallization unit, performing primary extraction crystallization separation, and using the filtrate separated by primary extraction crystallization to recover methanol in a rectifying tower;
continuously melting the crystals separated by the primary extraction crystallization, continuously adding the filtrate separated by the tertiary extraction crystallization into a secondary dissolution kettle, controlling the temperature to completely dissolve the crystals, and adding the filtrate into a secondary extraction crystallization unit to perform secondary extraction crystallization separation;
continuously melting the crystals separated by the secondary extraction crystallization, continuously adding the crystals and the methanol recovered by the rectifying tower into a three-time dissolution kettle, controlling the temperature to completely dissolve the crystals, and adding the crystals into a three-time extraction crystallization unit to perform three-time extraction crystallization separation;
and drying the crystals separated by three times of extraction crystallization to obtain the 2, 4-dinitrochlorobenzene product.
2. The process for the continuous purification of 2, 4-dinitrochlorobenzene according to claim 1, characterized in that the primary, secondary and tertiary extractive crystallization units each independently comprise 1 to 3 crystallizers.
3. The process for the continuous purification of 2, 4-dinitrochlorobenzene according to claim 1, characterized in that the rectification column heel is used for the production of sulphurised black.
4. The method for continuously purifying 2, 4-dinitrochlorobenzene according to claim 1, wherein the temperatures of the primary dissolution kettle, the secondary dissolution kettle and the tertiary dissolution kettle are respectively and independently controlled at 50-65 ℃.
5. The process for the continuous purification of 2, 4-dinitrochlorobenzene according to claim 1, characterized in that the content of 2, 4-dinitrochlorobenzene in the crude 2, 4-dinitrochlorobenzene is between 85% and 95% by weight.
6. The method for continuously purifying 2, 4-dinitrochlorobenzene according to claim 1, wherein the mass ratio of the crude 2, 4-dinitrochlorobenzene in the molten state or crystals to the filtrate or methanol added to the primary dissolution vessel, the secondary dissolution vessel or the tertiary dissolution vessel is 1:1.5 to 2.5, respectively.
7. The method for continuously purifying 2, 4-dinitrochlorobenzene according to claim 1, wherein the crystallization temperatures of the primary extraction crystallization unit, the secondary extraction crystallization unit and the tertiary extraction crystallization unit are respectively and independently controlled at-5 to 15 ℃, and the material residence time is respectively and independently controlled at 2 to 6 hours.
8. The process for the continuous purification of 2, 4-dinitrochlorobenzene according to claim 1, characterized in that the temperature of the reboiler of the rectification column is controlled between 65 and 85℃and the temperature of the top of the rectification column is controlled between 60 and 75 ℃.
9. A system for continuously purifying 2, 4-dinitrochlorobenzene is characterized by comprising a primary dissolution kettle, a secondary dissolution kettle and a tertiary dissolution kettle;
the primary dissolution kettle, the primary extraction crystallization unit and the primary filter are sequentially connected, and the primary filter is connected with a primary filtrate tank for collecting filtrate and a primary product buffer tank for collecting and heating molten crystals;
the secondary dissolution kettle, the secondary extraction crystallization unit and the secondary filter are sequentially connected, and the secondary filter is connected with a secondary filtrate tank for collecting filtrate and a secondary product buffer tank for collecting and heating molten crystals;
the third dissolution kettle, the third extraction crystallization unit and the third filter are sequentially connected, and the third filter is connected with a third filtrate tank for collecting filtrate and a third product tank for collecting and drying crystals;
the primary filtrate tank, the rectifying tower and the third dissolution kettle are connected in sequence; the third dissolution kettle is also connected with a secondary product buffer tank;
the secondary dissolution kettle is connected with the tertiary filtrate tank and the primary product buffer tank;
the primary dissolution kettle is connected with the secondary filtrate tank.
10. The system for continuously purifying 2, 4-dinitrochlorobenzene according to claim 9, wherein a methanol raw material tank is arranged between the rectifying tower and the third dissolution kettle;
the rectifying tower is also connected with a tail trough.
Priority Applications (1)
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