CN116444340B - Separation and purification method for mixed dichlorotoluene by coupling rectification and crystallization - Google Patents
Separation and purification method for mixed dichlorotoluene by coupling rectification and crystallization Download PDFInfo
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- 238000002425 crystallisation Methods 0.000 title claims abstract description 109
- 230000008025 crystallization Effects 0.000 title claims abstract description 109
- CAHQGWAXKLQREW-UHFFFAOYSA-N Benzal chloride Chemical compound ClC(Cl)C1=CC=CC=C1 CAHQGWAXKLQREW-UHFFFAOYSA-N 0.000 title claims abstract description 67
- 238000000926 separation method Methods 0.000 title claims abstract description 37
- 238000000034 method Methods 0.000 title claims abstract description 25
- 238000000746 purification Methods 0.000 title claims abstract description 20
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- 238000010168 coupling process Methods 0.000 title claims description 10
- 238000005859 coupling reaction Methods 0.000 title claims description 10
- 239000007788 liquid Substances 0.000 claims abstract description 45
- 239000011259 mixed solution Substances 0.000 claims abstract description 19
- KCXMKQUNVWSEMD-UHFFFAOYSA-N benzyl chloride Chemical compound ClCC1=CC=CC=C1 KCXMKQUNVWSEMD-UHFFFAOYSA-N 0.000 claims abstract description 5
- 238000004064 recycling Methods 0.000 claims abstract description 3
- FUNUTBJJKQIVSY-UHFFFAOYSA-N 2,4-Dichlorotoluene Chemical class CC1=CC=C(Cl)C=C1Cl FUNUTBJJKQIVSY-UHFFFAOYSA-N 0.000 claims description 26
- KFAKZJUYBOYVKA-UHFFFAOYSA-N 1,4-dichloro-2-methylbenzene Chemical class CC1=CC(Cl)=CC=C1Cl KFAKZJUYBOYVKA-UHFFFAOYSA-N 0.000 claims description 25
- 230000035900 sweating Effects 0.000 claims description 25
- 238000011084 recovery Methods 0.000 claims description 23
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 claims description 21
- 239000012452 mother liquor Substances 0.000 claims description 19
- 239000000047 product Substances 0.000 claims description 17
- WYUIWKFIFOJVKW-UHFFFAOYSA-N 1,2-dichloro-4-methylbenzene Chemical class CC1=CC=C(Cl)C(Cl)=C1 WYUIWKFIFOJVKW-UHFFFAOYSA-N 0.000 claims description 16
- DMEDNTFWIHCBRK-UHFFFAOYSA-N 1,3-dichloro-2-methylbenzene Chemical class CC1=C(Cl)C=CC=C1Cl DMEDNTFWIHCBRK-UHFFFAOYSA-N 0.000 claims description 11
- RYMMNSVHOKXTNN-UHFFFAOYSA-N 1,3-dichloro-5-methyl-benzene Chemical class CC1=CC(Cl)=CC(Cl)=C1 RYMMNSVHOKXTNN-UHFFFAOYSA-N 0.000 claims description 11
- 239000000243 solution Substances 0.000 claims description 10
- 238000002844 melting Methods 0.000 claims description 8
- 230000008018 melting Effects 0.000 claims description 8
- UHOVQNZJYSORNB-UHFFFAOYSA-N Benzene Chemical compound C1=CC=CC=C1 UHOVQNZJYSORNB-UHFFFAOYSA-N 0.000 claims description 6
- RTZKZFJDLAIYFH-UHFFFAOYSA-N Diethyl ether Chemical compound CCOCC RTZKZFJDLAIYFH-UHFFFAOYSA-N 0.000 claims description 6
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims description 6
- HEDRZPFGACZZDS-UHFFFAOYSA-N Chloroform Chemical compound ClC(Cl)Cl HEDRZPFGACZZDS-UHFFFAOYSA-N 0.000 claims description 4
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 4
- ZMXDDKWLCZADIW-UHFFFAOYSA-N N,N-Dimethylformamide Chemical compound CN(C)C=O ZMXDDKWLCZADIW-UHFFFAOYSA-N 0.000 claims description 4
- 239000013078 crystal Substances 0.000 claims description 4
- 238000000605 extraction Methods 0.000 claims description 4
- 239000002904 solvent Substances 0.000 claims description 4
- VZGDMQKNWNREIO-UHFFFAOYSA-N tetrachloromethane Chemical compound ClC(Cl)(Cl)Cl VZGDMQKNWNREIO-UHFFFAOYSA-N 0.000 claims description 4
- 150000001335 aliphatic alkanes Chemical class 0.000 claims description 2
- 230000006835 compression Effects 0.000 claims description 2
- 238000007906 compression Methods 0.000 claims description 2
- 239000012467 final product Substances 0.000 claims description 2
- 229920001084 poly(chloroprene) Polymers 0.000 claims description 2
- GWLKCPXYBLCEKC-UHFFFAOYSA-N 1,2-dichloro-3-methylbenzene Chemical class CC1=CC=CC(Cl)=C1Cl GWLKCPXYBLCEKC-UHFFFAOYSA-N 0.000 claims 7
- 210000004243 sweat Anatomy 0.000 claims 1
- 238000005265 energy consumption Methods 0.000 abstract description 6
- 150000003613 toluenes Chemical class 0.000 abstract 1
- 208000008454 Hyperhidrosis Diseases 0.000 description 21
- 239000000203 mixture Substances 0.000 description 17
- 238000005660 chlorination reaction Methods 0.000 description 10
- 230000008569 process Effects 0.000 description 9
- 239000002994 raw material Substances 0.000 description 7
- 238000001179 sorption measurement Methods 0.000 description 6
- 230000015572 biosynthetic process Effects 0.000 description 4
- 238000003786 synthesis reaction Methods 0.000 description 4
- NPDACUSDTOMAMK-UHFFFAOYSA-N 4-Chlorotoluene Chemical compound CC1=CC=C(Cl)C=C1 NPDACUSDTOMAMK-UHFFFAOYSA-N 0.000 description 3
- 239000003463 adsorbent Substances 0.000 description 3
- 239000003054 catalyst Substances 0.000 description 3
- 239000000543 intermediate Substances 0.000 description 3
- 239000002808 molecular sieve Substances 0.000 description 3
- URGAHOPLAPQHLN-UHFFFAOYSA-N sodium aluminosilicate Chemical compound [Na+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O URGAHOPLAPQHLN-UHFFFAOYSA-N 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- IBSQPLPBRSHTTG-UHFFFAOYSA-N 1-chloro-2-methylbenzene Chemical compound CC1=CC=CC=C1Cl IBSQPLPBRSHTTG-UHFFFAOYSA-N 0.000 description 2
- YYROPELSRYBVMQ-UHFFFAOYSA-N 4-toluenesulfonyl chloride Chemical compound CC1=CC=C(S(Cl)(=O)=O)C=C1 YYROPELSRYBVMQ-UHFFFAOYSA-N 0.000 description 2
- 238000009835 boiling Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- OPNQJIWBFJUXNO-UHFFFAOYSA-N 2,5-dichloro-5-methylcyclohexa-1,3-diene Chemical compound CC1(Cl)CC=C(Cl)C=C1 OPNQJIWBFJUXNO-UHFFFAOYSA-N 0.000 description 1
- FECNOIODIVNEKI-UHFFFAOYSA-N 2-[(2-aminobenzoyl)amino]benzoic acid Chemical class NC1=CC=CC=C1C(=O)NC1=CC=CC=C1C(O)=O FECNOIODIVNEKI-UHFFFAOYSA-N 0.000 description 1
- PLAZTCDQAHEYBI-UHFFFAOYSA-N 2-nitrotoluene Chemical compound CC1=CC=CC=C1[N+]([O-])=O PLAZTCDQAHEYBI-UHFFFAOYSA-N 0.000 description 1
- ZPTVNYMJQHSSEA-UHFFFAOYSA-N 4-nitrotoluene Chemical compound CC1=CC=C([N+]([O-])=O)C=C1 ZPTVNYMJQHSSEA-UHFFFAOYSA-N 0.000 description 1
- 230000004913 activation Effects 0.000 description 1
- 238000010420 art technique Methods 0.000 description 1
- 238000003795 desorption Methods 0.000 description 1
- 238000006193 diazotization reaction Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- SYSQUGFVNFXIIT-UHFFFAOYSA-N n-[4-(1,3-benzoxazol-2-yl)phenyl]-4-nitrobenzenesulfonamide Chemical class C1=CC([N+](=O)[O-])=CC=C1S(=O)(=O)NC1=CC=C(C=2OC3=CC=CC=C3N=2)C=C1 SYSQUGFVNFXIIT-UHFFFAOYSA-N 0.000 description 1
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- 239000007858 starting material Substances 0.000 description 1
- 230000002194 synthesizing effect Effects 0.000 description 1
- 238000010977 unit operation Methods 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
Classifications
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C17/00—Preparation of halogenated hydrocarbons
- C07C17/38—Separation; Purification; Stabilisation; Use of additives
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C17/00—Preparation of halogenated hydrocarbons
- C07C17/38—Separation; Purification; Stabilisation; Use of additives
- C07C17/383—Separation; Purification; Stabilisation; Use of additives by distillation
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C17/00—Preparation of halogenated hydrocarbons
- C07C17/38—Separation; Purification; Stabilisation; Use of additives
- C07C17/392—Separation; Purification; Stabilisation; Use of additives by crystallisation; Purification or separation of the crystals
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/10—Process efficiency
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- Crystallography & Structural Chemistry (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
The invention discloses a separation and purification method of mixed dichlorotoluene coupled with rectification and crystallization. Specifically, the mixed solution of the dichlorotoluene is subjected to rectification, crystallization, separation and purification, and each isomer is respectively purified and recovered. Firstly, removing light and heavy components such as chlorotoluene and polychlorinated toluene in the dichlorotoluene mixed solution through rectification separation, then carrying out preliminary separation through rectification, extracting enrichment liquid of each dichlorotoluene isomer at different positions of a rectifying section, ensuring that the concentration of the enrichment liquid is in a crystalline phase region corresponding to the dichlorotoluene isomer, respectively transferring the extracted five groups of enrichment liquid into a crystallization section, and improving the purity of the corresponding dichlorotoluene isomer to more than 99.5% through multistage melt crystallization, wherein the crystallization mother liquid can be returned to the rectification section for recycling dichlorotoluene. The separation process provided by the invention has the advantages of high product purity, simple separation process, safe operation, low energy consumption and the like.
Description
Technical Field
The invention belongs to the technical field of chemical separation, and particularly relates to a separation and purification method of mixed dichlorotoluene coupled with rectification and crystallization.
Background
Dichlorotoluene (DCT) is an important chemical intermediate that has six isomers, 2,3-DCT, 2,4-DCT, 2,5-DCT, 2,6-DCT, 3,4-DCT, and 3,5-DCT, respectively. Wherein the five isomers except 3,5-DCT are colorless transparent liquid at room temperature. Different isomers often have different uses, such as dye intermediates, pharmaceutical intermediates, pesticide intermediates, and the like. The separation difficulty of the dichlorotoluene is high because the physical properties of the dichlorotoluene isomers are very similar. At present, different dichlorotoluene isomers are mainly synthesized by directional chlorination. For example, 2,4-DCT is usually prepared by using p-chlorotoluene as a starting material, performing chlorination reaction in the presence of a catalyst to generate a mixture of 2,4-DCT and 3,4-DCT, and then rectifying and separating to obtain a 2,4-DCT product. For another example, the 2,6-DCT can be prepared by adopting a p-toluenesulfonyl chloride directional chlorination method, or can be prepared by adopting o-nitrotoluene and p-nitrotoluene through chlorination, reduction and diazotization reactions. It can be seen that, in order to obtain a specific dichlorotoluene configuration, there is often a specific requirement for radical occupation of the synthetic raw material, and a certain amount of mixed dichlorotoluene is still produced due to the fact that the selectivity of the chlorination reaction cannot reach 100% in the synthetic process. These drawbacks all increase to some extent the production costs of dichlorotoluene.
From the molecular structure, toluene is used as a raw material to prepare the dichlorotoluene through directional chlorination reaction, so that the preparation method is a simpler synthetic route. But limited by the selectivity of the catalyst, the toluene chlorination reaction at present has low selectivity to form dichlorotoluene, and generally forms a mixture of five isomers. Therefore, if the mixed dichlorotoluene can be separated and purified in a relatively economical way to obtain high-purity products of all isomers, the synthesis process of the dichlorotoluene can be thoroughly changed, and the production cost and the energy consumption are reduced.
CN20081010184. X (Chinese patent application publication No. CN101633601A, publication date 1 month 27 of 2010) is considered as the closest prior art of the present invention, and discloses a method for industrially producing 2, 6-dichlorotoluene. Firstly, 2-chlorotoluene is taken as a raw material, mixed liquor of dichlorotoluene is obtained through chlorination reaction, and then 2, 6-dichlorotoluene with purity more than or equal to 99.0% is obtained through rectification, melting crystallization, separation and purification. But the method adopts 2-chlorotoluene as a raw material to generate dichlorotoluene through chlorination reaction, the composition of the dichlorotoluene mixed solution formed by the synthesis process is relatively simple, 3, 4-dichlorotoluene is not contained, the specific composition range of each isomer is not limited, a specific catalyst is needed to ensure that the content of 2,6-DCT in the product is relatively high, then 2,6-DCT is recovered only through two-step rectification and two-step crystallization separation under the condition that the content of 2,6-DCT is relatively high, and a specific scheme is not provided for the separation and purification of the rest mixed dichlorotoluene. In addition, CN201510864787.0 (chinese patent application publication No. CN105399601a, publication date 2016, 3, 16) discloses a method for separating mixed dichlorotoluene. The method adopts a rectification-crystallization-adsorption separation combined mode to separate the mixed dichlorotoluene isomer, and the process is more complex than the invention. In particular, the molecular sieve adsorbent is adopted in the adsorption section, the adsorption condition is severe, high-temperature and high-pressure conditions are often needed, meanwhile, the continuous operation time of the adsorbent is short, the activation and regeneration are often needed under the complex conditions of high temperature and high pressure, the whole process is complex, and the energy consumption is high. In addition, there are a large number of prior art techniques for separating and purifying dichlorotoluene by molecular sieve adsorption, such as US4254062 (U.S. patent application, publication date 3/1981), EP0249883 (european patent application, publication date 12/23/1987), US4922040 (U.S. patent application, publication date 5/1/1990), and the like. But has the problems of high separation energy consumption, low yield, certain concentration requirement on the feed composition, service life of the molecular sieve and the like from the technical effect.
Disclosure of Invention
Based on the problems in the field of dichlorotoluene synthesis, the invention provides a method for separating and purifying mixed dichlorotoluene by coupling rectification and crystallization. Firstly, coarse separation is carried out on mixed dichlorotoluene through rectification, the concentration ratio of different isomers is adjusted, a dichlorotoluene mixed solution with higher specific molecular configuration content is extracted at different positions of a rectification section, and then the mixed solution is further separated and purified through melt crystallization, so that a corresponding high-purity dichlorotoluene product is obtained. The mixed dichlorotoluene contains five isomers, so that the five-element solid-liquid equilibrium phase diagram is complex, and no document reports exist. Therefore, the process of completely separating and purifying five isomers by adopting melt crystallization is not reported in the literature.
The invention creatively proposes to separate and purify the five isomers of the p-dichlorotoluene by adopting a rectification coupling melt crystallization process according to the gas-liquid and solid-liquid balance characteristics of a five-membered isomer system from basic thermodynamic balance data, and has the advantages of simple process route, low operation cost, high product purity and the like. The separation process provided by the invention can be used for directly synthesizing the dichlorotoluene by toluene chlorination, so that the traditional synthesis process of the dichlorotoluene is thoroughly changed.
The specific technical scheme of the invention is as follows:
a separation and purification method of mixed dichlorotoluene coupled with rectification and crystallization is characterized in that the mixed solution of dichlorotoluene contains five isomers of 2,4-DCT, 2,5-DCT, 2,6-DCT, 2,3-DCT and 3,4-DCT, firstly, the mixed solution of dichlorotoluene is guided into a first rectifying tower for primary separation, the mixed solution of 2,4-DCT, 2,5-DCT and 2,6-DCT is extracted from the tower top, the mixed solution of 2,3-DCT and 3,4-DCT is extracted from the tower bottom, the first rectifying tower top is extracted into a second rectifying tower, the 2,4-DCT and 2,6-DCT enrichment solution is extracted from the tower top of the second rectifying tower, the 2,5-DCT enrichment solution is extracted from the tower bottom of the second rectifying tower, the 2, 3-enrichment solution is extracted from the tower bottom of the third rectifying tower, extracting 3,4-DCT enrichment liquid from the tower bottom of the third rectifying tower, extracting 2,6-DCT enrichment liquid from the tower top of the fourth rectifying tower, extracting 2,4-DCT enrichment liquid from the tower bottom of the fourth rectifying tower, crystallizing and separating 2,6-DCT in the first crystallization section, returning crystallization mother liquor to the fourth rectifying tower, crystallizing and separating 2,4-DCT in the tower bottom of the fourth rectifying tower, returning crystallization mother liquor to the second rectifying tower, crystallizing and separating 2,5-DCT in the third crystallization section, returning crystallization mother liquor to the second rectifying tower, returning crystallization mother liquor to the tower top of the third rectifying tower, recovering 2, the 3-DCT enrichment liquid enters a fourth crystallization section to crystallize and separate 2,3-DCT, the crystallization mother liquor returns to a third rectifying tower, the 3,4-DCT enrichment liquid extracted from the tower bottom of the third rectifying tower enters a fifth crystallization section to crystallize and separate 3,4-DCT, and the crystallization mother liquor returns to the third rectifying tower.
Preferably, the 2,5-DCT content in the 2,5-DCT enrichment liquid extracted from the tower bottom of the second rectifying tower is more than 45%, the 2,3-DCT content in the 2,3-DCT enrichment liquid extracted from the tower top of the third rectifying tower is more than 50%, the 3,4-DCT content in the 3,4-DCT enrichment liquid extracted from the tower bottom of the third rectifying tower is more than 70%, the 2,6-DCT content in the 2,6-DCT enrichment liquid extracted from the tower top of the fourth rectifying tower is more than 55%, and the 2,4-DCT content in the 2,4-DCT enrichment liquid extracted from the tower bottom of the fourth rectifying tower is more than 75%.
Preferably, each rectifying tower is operated under negative pressure, the tower pressure is 0-50Kpa, the tower bottom temperature of the first rectifying tower is 80-180 ℃, the tower top temperature is 50-175 ℃, the tower bottom temperature of the second rectifying tower is 80-180 ℃, the tower top temperature is 50-175 ℃, the tower bottom temperature of the third rectifying tower is 80-200 ℃, the tower top temperature is 50-190 ℃, the tower bottom temperature of the fourth rectifying tower is 80-180 ℃, and the tower top temperature is 50-175 ℃.
Preferably, each rectifying tower adopts a heat pump for heat recycling, the heat pump adopts a mechanical vapor compression mode, the compressor mode is centrifugal, screw or Roots type, and the heat pump mode adopts single tower top tower kettle coupling or multi-tower top tower kettle coupling.
Preferably, each crystallization section adopts a multi-stage melting crystallization form, the whole crystallization section is divided into a recovery section, a purification section and a sweating section, the corresponding dichlorotoluene isomer enrichment liquid enters the crystallization section at an intermediate stage, the recovery section is arranged below a feeding stage, the purification section is arranged above the feeding stage, the final product extraction stage is the sweating section, each stage of crystallization section has temperature and concentration gradient, each stage of crystals are gradually transferred upwards to the upper stage, each stage of crystallization mother liquor is gradually transferred downwards to the lower stage, the crystals finally realize melting sweating in the sweating section, the sweating liquid returns to the last stage of crystallization in the purification section, the product with the purity of more than 99.5 percent corresponding dichlorotoluene isomer is extracted, and the crystallization mother liquor of the last stage of crystallization in the recovery section returns to the corresponding rectification tower.
Preferably, the balance temperature of the last-stage crystallizer of the first crystallization section recovery section is-40 to-2 ℃, the perspiration temperature of the perspiration section is 1 to 8 ℃, the balance temperature of the last-stage crystallizer of the second crystallization section recovery section is-35 to-16 ℃, the perspiration temperature of the perspiration section is-14 to-6 ℃, the balance temperature of the last-stage crystallizer of the third crystallization section recovery section is-30 to 0 ℃, the perspiration temperature of the perspiration section is 2 to 8 ℃, the balance temperature of the last-stage crystallizer of the fourth crystallization section recovery section is-35 to 0 ℃, the perspiration temperature of the perspiration section is 3 to 10 ℃, the balance temperature of the last-stage crystallizer of the fifth crystallization section recovery section is-35 to-18 ℃, and the perspiration temperature of the perspiration section is-16 to-8 ℃.
Preferably, the crystallization section adjusts the phase equilibrium relationship by adding a solvent when the corresponding dichlorotoluene isomer is crystallized at high concentration, wherein the solvent is one or more of methanol, ethanol, DMF, chloroform, benzene, toluene, chlorotoluene, diethyl ether, liquid alkane of C5-C16 or carbon tetrachloride.
Preferably, the mixed solution of the dichlorotoluene further contains light and heavy components such as toluene, chlorotoluene, polychloroprene and the like, the light and heavy components mixed in the mixed dichlorotoluene are removed through a light removal tower and a heavy removal tower before entering the first rectifying tower, and then the mixed dichlorotoluene enters the first rectifying tower for separation and purification.
The invention has the remarkable technical effects that:
the invention has the advantages of low equipment investment, safe operation, low equipment material requirement and low corrosiveness, and the rectification section adopts negative pressure operation, the pressure and the temperature are lower, and the crystallization section operates at low temperature under normal pressure, so that the rectification and the crystallization are unit operation means widely used in the chemical industry. Compared with the separation method adopting high-temperature high-pressure adsorption and desorption in the prior art, the equipment investment and the operation energy consumption are greatly reduced.
The operation cost is low, the heat pump technology is adopted to recycle the energy at the top of the rectifying tower for the use of the tower kettle, and the heat exchange network between each two crystallization stages can be optimized according to the temperature gradient, so that the operation energy consumption is greatly reduced.
Environmental protection and safety, and no consumable. Compared with the extraction rectification and the like in the prior art, the technical scheme of the invention does not need to add an organic extractant, does not need to consume an adsorbent compared with an adsorption separation process, does not generate solid, liquid and gas waste, and is more environment-friendly.
The separation degree is good, the product purity is high, the separation among all five isomers can be realized, and the prior art can only selectively separate one or more isomers, so that the complete separation cannot be realized. By optimizing the crystallization stage operating parameters and the design of the stage number, the dichlorotoluene product with the purity of 99.5 percent to higher can be provided.
Drawings
FIG. 1 is a flow chart of a separation process;
FIG. 2 is a flow chart of a multistage melt crystallization stage.
Detailed Description
In order to more clearly illustrate the technical solution of the present invention, the following specific embodiments of the related technical solution are given in conjunction with the description, it should be understood that the following embodiments do not limit the scope of the present invention, and any technical solution formed by evolution and improvement of the related technical solution based on the present invention without any inventive effort belongs to the scope of the present invention.
Example 1
The mixed dichlorotoluene with the composition shown in the table-1 is led into a first rectifying tower for separation after light and heavy removal, the total content of 2,4-DCT, 2,5-DCT and 2,6-DCT in the tower top produced flow accounts for about 98 percent, and the total content of 2,3-DCT and 3,4-DCT in the tower bottom produced flow accounts for about 94 percent. And (3) extracting the tower top of the first rectifying tower and introducing the extracted tower top of the first rectifying tower into a second rectifying tower, and extracting the tower bottom of the first rectifying tower and introducing the extracted tower bottom of the first rectifying tower into a third rectifying tower. The second rectifying column overhead stream contained about 61% 2,4-DCT, 30% 2,6-DCT and 7% 2,5-DCT. The second rectifying column bottoms stream contained about 4% 2,4-DCT, 3% 2,6-DCT and 91% 2,5-DCT. And the top of the second rectifying tower is extracted into a fourth rectifying tower. The fourth rectifying column overhead stream contains about 8% 2,4-DCT, 90% 2,6-DCT, and 2% 2,5-DCT. The fourth rectifying column bottoms stream contained about 86% 2,4-DCT, 2% 2,6-DCT and 9% 2,5-DCT. The third rectifying column overhead stream contained about 77% 2,3-DCT and 10% 3,4-DCT. The third rectifying column bottoms stream contained about 14% 2,3-DCT and 81% 3,4-DCT. The 2,6-DCT enriched liquid extracted from the top of the fourth rectifying tower enters a first crystallization section for multi-stage melt crystallization, the first crystallization section is provided with three-stage crystallization and one-stage sweating, the balance temperature of a last stage crystallizer of a recovery section is minus 16 ℃, the 2,6-DCT content in crystallization mother liquor is 70%, the temperature of the sweating stage is 3 ℃, and the product purity is 99.7%. And 2,4-DCT enriched liquid extracted from the tower bottom of the fourth rectifying tower enters a second crystallization section for multi-stage melt crystallization, seven stages of crystallization and primary sweating are arranged in the second crystallization section, the balance temperature of a last stage crystallizer of the recovery section is minus 20 ℃, the 2,4-DCT content in the crystallization mother liquor is 78%, the temperature of the sweating stage is minus 10 ℃, and the product purity is 99.6%. And 2,5-DCT enriched liquid extracted from the tower bottom of the second rectifying tower enters a third crystallization section for multi-stage melt crystallization, four-stage crystallization and primary sweating are arranged in the third crystallization section, the balance temperature of a last stage crystallizer of the recovery section is-7 ℃, the 2,5-DCT content in the crystallization mother liquor is 70%, the temperature of the sweating stage is 5 ℃, and the product purity is 99.5%. The 2,3-DCT enriched liquid extracted from the top of the third rectifying tower enters a fourth crystallization section for multi-stage melting crystallization, the fourth crystallization section is provided with six stages of crystallization and one stage of sweating, the balance temperature of a last stage of crystallizer of the recovery section is-17 ℃, the 2,3-DCT content in the crystallization mother liquor is 65%, the temperature of the sweating stage is 7 ℃, and the purity of the product is 99.8%. And (3) introducing the 3,4-DCT enriched liquid extracted from the tower bottom of the third rectifying tower into a fifth crystallization section for multistage melt crystallization, wherein the fifth crystallization section is provided with four-stage crystallization and one-stage sweating, the balance temperature of a last-stage crystallizer of the recovery section is-27 ℃, the 3,4-DCT content in the crystallization mother liquor is 70%, the temperature of the sweating stage is-12 ℃, and the product purity is 99.7%.
Table-1 mixed dichlorotoluene composition A.
| Numbering device | P-chlorotoluene wt% | 2,4-DCTwt% | 2,6-DCTwt% | 2,5-DCTwt | 2,3-DCT wt% | 3,4-DCT wt% | High boiling impurities wt% |
| Composition of raw materials | 0.95 | 22 | 11 | 43 | 7 | 15 | 1.05 |
Examples
It should be pointed out that the technical scheme provided by the invention is not only suitable for separating the mixed solution containing all five types of dichlorotoluene isomers, but also can be adopted for separating the mixed solution containing only part of dichlorotoluene isomers, and the corresponding extraction of the rectifying section and the corresponding crystallization section are correspondingly canceled. In this example, a separation process of a mixed solution of dichlorotoluene containing a part of isomers was described as a raw material.
The mixed dichlorotoluene with the composition shown in the table-2 enters a first rectifying tower for primary separation, the tower top is used for extracting 2,6-DCT with the composition of 63 percent, 2,5-DCT with the composition of 35 percent and 2,3-DCT with the composition of 2 percent, and the tower bottom is used for extracting 2,6-DCT with the composition of 1 percent, 2,5-DCT with the composition of 4 percent and 2,3-DCT with the composition of 95 percent. The first rectifying tower overhead is extracted into a second rectifying tower, the second rectifying tower overhead is extracted into 96% of 2,6-DCT, 3% of 2,5-DCT and 1% of 2,3-DCT, and the tower bottom is extracted into 4% of 2,6-DCT, 92% of 2,5-DCT and 4% of 2,3-DCT. The tower top of the second rectifying tower is extracted into a first crystallization section for multistage melting crystallization separation and purification, the first crystallization section is provided with three-stage crystallization and one-stage sweating, the balance temperature of a last stage crystallizer of a recovery section is-13 ℃, the 2,6-DCT content in crystallization mother liquor is 75%, the temperature of the sweating stage is 4 ℃, and the purity of the product is 99.8%. The second rectifying tower is extracted from the tower bottom and enters a second crystallization section for multistage melting crystallization separation and purification, the second crystallization section is provided with five stages of crystallization and primary sweating, the balance temperature of a last stage crystallizer of the recovery section is-7 ℃, the 2,5-DCT content in the crystallization mother liquor is 70%, the temperature of the sweating stage is 4 ℃, and the purity of the product is 99.6%. The first rectifying tower is extracted from the tower bottom and enters a third crystallization section for multi-stage melting crystallization separation and purification, the third crystallization section is provided with three-stage crystallization and one-stage sweating, the balance temperature of a last stage crystallizer of the recovery section is-3 ℃, the 2,3-DCT content in the crystallization mother liquor is 85%, the temperature of the sweating stage is 7 ℃, and the purity of the product is 99.7%.
Table-2 mixed dichlorotoluene composition B.
| Numbering device | P-chlorotoluene wt% | 2,4-DCTwt% | 2,6-DCTwt% | 2,5-DCTwt | 2,3-DCT wt% | 3,4-DCT wt% | High boiling impurities wt% |
| Composition of raw materials | 0 | 0 | 37 | 22 | 41 | 0 | 0 |
Claims (5)
1. A separation and purification method of mixed dichlorotoluene coupled with rectification and crystallization is characterized in that the mixed solution of dichlorotoluene contains five isomers of 2, 4-dichlorotoluene, 2, 5-dichlorotoluene, 2, 6-dichlorotoluene, 2, 3-dichlorotoluene and 3, 4-dichlorotoluene, firstly, the mixed solution of dichlorotoluene is introduced into a first rectifying tower for primary separation, the mixed solution of 2, 4-dichlorotoluene, 2, 5-dichlorotoluene and 2, 6-dichlorotoluene is extracted from the tower top, the mixed solution of 2, 3-dichlorotoluene and 3, 4-dichlorotoluene is extracted from the tower bottom, the first rectifying tower top is extracted into a second rectifying tower, the enriched solution of 2, 4-dichlorotoluene and 2, 6-dichlorotoluene is extracted from the tower top of the second rectifying tower, the enriched solution of 2, 5-dichlorotoluene is extracted from the tower bottom of the second rectifying tower, the first rectifying tower kettle is extracted into a third rectifying tower, the third rectifying tower kettle is extracted into a 2, 3-dichlorotoluene enrichment liquid, the third rectifying tower kettle is extracted into a 3, 4-dichlorotoluene enrichment liquid, the second rectifying tower kettle is extracted into a fourth rectifying tower, the fourth rectifying tower kettle is extracted into a 2, 6-dichlorotoluene enrichment liquid, the fourth rectifying tower kettle is extracted into a 2, 4-dichlorotoluene enrichment liquid, the 2, 6-dichlorotoluene enrichment liquid extracted from the fourth rectifying tower kettle is introduced into a first crystallization section to crystallize and separate 2, 6-dichlorotoluene, the crystallization mother liquor is returned to the fourth rectifying tower, the 2, 4-dichlorotoluene enrichment liquid extracted from the fourth rectifying tower kettle is introduced into a second crystallization section to crystallize and separate 2, 4-dichlorotoluene, the crystallization is returned to the second rectifying tower, the 2, 6-dichlorotoluene extracted from the second rectifying tower kettle, the enriched liquid of 5-dichlorotoluene enters a third crystallization section to separate 2, 5-dichlorotoluene by crystallization, the crystallized mother liquid returns to a second rectifying tower, the enriched liquid of 2, 3-dichlorotoluene extracted from the top of the third rectifying tower enters a fourth crystallization section to separate 2, 3-dichlorotoluene by crystallization, the crystallized mother liquid returns to the third rectifying tower, the enriched liquid of 3, 4-dichlorotoluene extracted from the bottom of the third rectifying tower enters a fifth crystallization section to separate 3, 4-dichlorotoluene by crystallization, the crystallized mother liquid returns to the third rectifying tower, wherein each rectifying tower adopts negative pressure operation, the tower pressure is 0-50Kpa, the temperature of the bottom of the first rectifying tower is 80-180 ℃, the temperature of the top of the second rectifying tower is 50-175 ℃, the temperature of the bottom of the second rectifying tower is 80-180 ℃, the temperature of the top of the third rectifying tower is 80-200 ℃, the temperature of the top of the third rectifying tower is 50-190 ℃, the temperature of the tower bottom of the fourth rectifying tower is 80-180 ℃, the temperature of the tower top is 50-175 ℃, the whole crystallizing section is divided into a recovery section, a purification section and a sweating section, the corresponding enriched solution of the dichlorotoluene isomer enters the crystallizing section at the middle stage, the recovery section is arranged below the feeding stage, the purification section is arranged above the feeding stage, the final product extraction stage is the sweating section, each stage of the crystallizing section has temperature and concentration gradient, each stage of crystals are gradually transferred upwards to the upper stage, each stage of crystallization mother liquor is gradually transferred downwards to the lower stage, the crystals finally realize melting sweating in the sweating section, the sweat returns to the final stage of the purifying section, the product with the purity of the corresponding dichlorotoluene isomer of more than 99.5 percent is extracted, the crystallization mother liquor of the final stage of the recovering section returns to the corresponding rectifying tower, the balance temperature of the last-stage crystallizer of the first crystallization section recovery section is-40 to-2 ℃, the perspiration temperature of the perspiration section is 1 to 8 ℃, the balance temperature of the last-stage crystallizer of the second crystallization section recovery section is-35 to-16 ℃, the perspiration temperature of the perspiration section is-14 to-6 ℃, the balance temperature of the last-stage crystallizer of the third crystallization section recovery section is-30 to 0 ℃, the perspiration temperature of the perspiration section is 2 to 8 ℃, the balance temperature of the last-stage crystallizer of the fourth crystallization section recovery section is-35 to 0 ℃, the perspiration temperature of the perspiration section is 3 to 10 ℃, the balance temperature of the last-stage crystallizer of the fifth crystallization section recovery section is-35 to-18 ℃, and the perspiration temperature of the perspiration section is-16 to-8 ℃.
2. The separation and purification method of mixed dichlorotoluene coupled with rectification and crystallization according to claim 1, wherein the content of 2, 5-dichlorotoluene in the 2, 5-dichlorotoluene enrichment liquid extracted from the tower bottom of the second rectification tower is more than 45%, the content of 2, 3-dichlorotoluene in the 2, 3-dichlorotoluene enrichment liquid extracted from the tower top of the third rectification tower is more than 50%, the content of 3, 4-dichlorotoluene in the 3, 4-dichlorotoluene enrichment liquid extracted from the tower bottom of the third rectification tower is more than 70%, the content of 2, 6-dichlorotoluene in the 2, 6-dichlorotoluene enrichment liquid extracted from the tower top of the fourth rectification tower is more than 55%, and the content of 2, 4-dichlorotoluene in the 2, 4-dichlorotoluene enrichment liquid extracted from the tower bottom of the fourth rectification tower is more than 75%.
3. The method for separating and purifying mixed dichlorotoluene by coupling rectification and crystallization according to claim 2, wherein each rectification tower adopts a heat pump for heat recycling, the heat pump adopts a mechanical vapor compression mode, a compressor mode is centrifugal, screw or Roots type, and the heat pump mode adopts single tower top tower kettle coupling or multi-tower top tower kettle coupling.
4. The method for separating and purifying mixed dichlorotoluene by coupling rectification and crystallization according to claim 3, wherein the crystallization section adjusts the phase equilibrium relationship by adding a solvent when the corresponding dichlorotoluene isomer is crystallized at high concentration, wherein the solvent is one or more of methanol, ethanol, DMF, chloroform, benzene, toluene, chlorotoluene, diethyl ether, liquid alkane of C5-C16 or carbon tetrachloride.
5. The method for separating and purifying mixed dichlorotoluene coupled with rectification and crystallization according to claim 4, wherein the mixed solution of dichlorotoluene further comprises light and heavy components of toluene, chlorotoluene and polychloroprene, the light and heavy components mixed in the mixed dichlorotoluene are removed by a light removal tower and a heavy removal tower before entering the first rectifying tower, and then the mixed solution of dichlorotoluene enters the first rectifying tower for separation and purification.
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Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102311306A (en) * | 2010-06-29 | 2012-01-11 | 中国石油化工股份有限公司 | Method for separating dichlorotoluene isomer through absorption |
| CN105399597A (en) * | 2015-12-01 | 2016-03-16 | 南京钟腾化工有限公司 | Method for separating mixed dichlorotoluene |
| CN105399601A (en) * | 2015-12-01 | 2016-03-16 | 南京钟腾化工有限公司 | Separation method of mixed dichlorotoluene |
| CN113429258A (en) * | 2021-06-17 | 2021-09-24 | 江苏超跃化学有限公司 | Method for separating dichlorotoluene mixture |
| CN116063144A (en) * | 2022-12-29 | 2023-05-05 | 柳州东风容泰化工股份有限公司 | Method for producing 2, 4-dichlorotoluene |
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Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102311306A (en) * | 2010-06-29 | 2012-01-11 | 中国石油化工股份有限公司 | Method for separating dichlorotoluene isomer through absorption |
| CN105399597A (en) * | 2015-12-01 | 2016-03-16 | 南京钟腾化工有限公司 | Method for separating mixed dichlorotoluene |
| CN105399601A (en) * | 2015-12-01 | 2016-03-16 | 南京钟腾化工有限公司 | Separation method of mixed dichlorotoluene |
| CN113429258A (en) * | 2021-06-17 | 2021-09-24 | 江苏超跃化学有限公司 | Method for separating dichlorotoluene mixture |
| CN116063144A (en) * | 2022-12-29 | 2023-05-05 | 柳州东风容泰化工股份有限公司 | Method for producing 2, 4-dichlorotoluene |
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