CN110128240B - Method for separating p-chlorobromobenzene and o-chlorobromobenzene by suspension melting crystallization method - Google Patents
Method for separating p-chlorobromobenzene and o-chlorobromobenzene by suspension melting crystallization method Download PDFInfo
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- CN110128240B CN110128240B CN201910516479.7A CN201910516479A CN110128240B CN 110128240 B CN110128240 B CN 110128240B CN 201910516479 A CN201910516479 A CN 201910516479A CN 110128240 B CN110128240 B CN 110128240B
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- chlorobromobenzene
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- NHDODQWIKUYWMW-UHFFFAOYSA-N 1-bromo-4-chlorobenzene Chemical compound ClC1=CC=C(Br)C=C1 NHDODQWIKUYWMW-UHFFFAOYSA-N 0.000 title claims abstract description 99
- QBELEDRHMPMKHP-UHFFFAOYSA-N 1-bromo-2-chlorobenzene Chemical compound ClC1=CC=CC=C1Br QBELEDRHMPMKHP-UHFFFAOYSA-N 0.000 title claims abstract description 52
- 238000002425 crystallisation Methods 0.000 title claims abstract description 49
- 238000000034 method Methods 0.000 title claims abstract description 43
- 239000000725 suspension Substances 0.000 title claims abstract description 31
- 238000002844 melting Methods 0.000 title claims abstract description 24
- 230000008018 melting Effects 0.000 title claims abstract description 24
- 239000007788 liquid Substances 0.000 claims abstract description 70
- 239000013078 crystal Substances 0.000 claims abstract description 57
- 238000001816 cooling Methods 0.000 claims abstract description 43
- 238000010438 heat treatment Methods 0.000 claims abstract description 31
- 230000008025 crystallization Effects 0.000 claims abstract description 29
- 239000006185 dispersion Substances 0.000 claims abstract description 24
- 239000000155 melt Substances 0.000 claims abstract description 14
- 230000008569 process Effects 0.000 claims abstract description 14
- 238000005406 washing Methods 0.000 claims abstract description 14
- 238000001035 drying Methods 0.000 claims abstract description 13
- 239000000203 mixture Substances 0.000 claims abstract description 13
- 238000001914 filtration Methods 0.000 claims abstract description 4
- 238000000967 suction filtration Methods 0.000 claims description 12
- 238000003756 stirring Methods 0.000 claims description 8
- 230000009467 reduction Effects 0.000 claims description 5
- 230000001105 regulatory effect Effects 0.000 claims description 2
- 239000012452 mother liquor Substances 0.000 abstract description 11
- 238000000926 separation method Methods 0.000 abstract description 10
- 239000000047 product Substances 0.000 description 24
- ALINVVBOLJMYOC-UHFFFAOYSA-N bromobenzene;hydrochloride Chemical compound Cl.BrC1=CC=CC=C1 ALINVVBOLJMYOC-UHFFFAOYSA-N 0.000 description 10
- 238000002156 mixing Methods 0.000 description 10
- 238000004064 recycling Methods 0.000 description 10
- 230000035900 sweating Effects 0.000 description 10
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 10
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 6
- 239000012535 impurity Substances 0.000 description 5
- 238000004519 manufacturing process Methods 0.000 description 5
- 238000000746 purification Methods 0.000 description 5
- 230000009286 beneficial effect Effects 0.000 description 4
- 230000008901 benefit Effects 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 3
- 230000001276 controlling effect Effects 0.000 description 3
- 239000000543 intermediate Substances 0.000 description 3
- 239000002245 particle Substances 0.000 description 3
- JBLSZOJIKAQEKG-UHFFFAOYSA-N phenyl hypobromite Chemical compound BrOC1=CC=CC=C1 JBLSZOJIKAQEKG-UHFFFAOYSA-N 0.000 description 3
- QARVLSVVCXYDNA-UHFFFAOYSA-N bromobenzene Chemical compound BrC1=CC=CC=C1 QARVLSVVCXYDNA-UHFFFAOYSA-N 0.000 description 2
- 239000012043 crude product Substances 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 238000010899 nucleation Methods 0.000 description 2
- 230000006911 nucleation Effects 0.000 description 2
- 239000003960 organic solvent Substances 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 239000005740 Boscalid Substances 0.000 description 1
- WKBOTKDWSSQWDR-UHFFFAOYSA-N Bromine atom Chemical compound [Br] WKBOTKDWSSQWDR-UHFFFAOYSA-N 0.000 description 1
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 1
- OFOBLEOULBTSOW-UHFFFAOYSA-N Propanedioic acid Natural products OC(=O)CC(O)=O OFOBLEOULBTSOW-UHFFFAOYSA-N 0.000 description 1
- 230000000844 anti-bacterial effect Effects 0.000 description 1
- 239000003899 bactericide agent Substances 0.000 description 1
- YWGDOWXRIALTES-NRFANRHFSA-N bepotastine Chemical compound C1CN(CCCC(=O)O)CCC1O[C@H](C=1N=CC=CC=1)C1=CC=C(Cl)C=C1 YWGDOWXRIALTES-NRFANRHFSA-N 0.000 description 1
- 229960002071 bepotastine Drugs 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- WYEMLYFITZORAB-UHFFFAOYSA-N boscalid Chemical compound C1=CC(Cl)=CC=C1C1=CC=CC=C1NC(=O)C1=CC=CN=C1Cl WYEMLYFITZORAB-UHFFFAOYSA-N 0.000 description 1
- 229940118790 boscalid Drugs 0.000 description 1
- GDTBXPJZTBHREO-UHFFFAOYSA-N bromine Substances BrBr GDTBXPJZTBHREO-UHFFFAOYSA-N 0.000 description 1
- 229910052794 bromium Inorganic materials 0.000 description 1
- FGZQJFGRLGJWBH-UHFFFAOYSA-N bromobenzene;dihydrochloride Chemical compound Cl.Cl.BrC1=CC=CC=C1 FGZQJFGRLGJWBH-UHFFFAOYSA-N 0.000 description 1
- 230000005465 channeling Effects 0.000 description 1
- 239000013064 chemical raw material Substances 0.000 description 1
- 239000000498 cooling water Substances 0.000 description 1
- 238000004134 energy conservation Methods 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 239000002360 explosive Substances 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- VZCYOOQTPOCHFL-UPHRSURJSA-N maleic acid Chemical compound OC(=O)\C=C/C(O)=O VZCYOOQTPOCHFL-UPHRSURJSA-N 0.000 description 1
- 239000011976 maleic acid Substances 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 239000000575 pesticide Substances 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000001953 recrystallisation Methods 0.000 description 1
- 238000011946 reduction process Methods 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- VZCYOOQTPOCHFL-UHFFFAOYSA-N trans-butenedioic acid Natural products OC(=O)C=CC(O)=O VZCYOOQTPOCHFL-UHFFFAOYSA-N 0.000 description 1
- 238000001132 ultrasonic dispersion Methods 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
- C07C17/392—Separation; Purification; Stabilisation; Use of additives by crystallisation; Purification or separation of the crystals
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Analytical Chemistry (AREA)
- Crystallography & Structural Chemistry (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
The invention provides a method for separating p-bromochlorobenzene and o-bromochlorobenzene by a suspension melting crystallization method, which comprises the following steps: ultrasonically dispersing a solid-liquid mixture of o-bromochloro-benzene and p-bromochloro-benzene for 25-35min to obtain a dispersion liquid; adding the dispersion liquid into a melt crystallizer, and heating to 60-75 ℃ to obtain mixed molten liquid; and cooling the mixed molten liquid to-10-20 ℃ at a cooling rate of 0.05-0.5 ℃/min, growing crystals for 1-6h, filtering, washing and drying to obtain the p-chlorobromobenzene. The separation method of the p-bromochloro-benzene and the o-bromochloro-benzene provided by the invention realizes separation of the p-bromochloro-benzene and the o-bromochloro-benzene isomers by designing a reasonable crystallization process route and controlling crystallization process conditions, and avoids the problems of serious occlusion of mother liquor and low product purity in the crystallization process of a common melt crystallization method by controlling the cooling rate and the crystal growing temperature, wherein the purity of the p-bromochloro-benzene can reach more than 99%, and the single-pass yield can reach 66.1% at most.
Description
Technical Field
The invention relates to the technical field of chemical separation and purification, in particular to a method for separating p-bromochlorobenzene and o-bromochlorobenzene by a suspension melting crystallization method.
Background
The p-chlorobromobenzene, also known as 4-chlorobromobenzene, is an important organic chemical raw material and is mainly used as a solvent and a pharmaceutical chemical synthesis intermediate. The bromobenzene dichloride can be mainly used for preparing pesticide bactericides such as boscalid intermediates and bepotastine intermediates and used as an important raw material of the maleic acid kaxamine, and has very important functions in the field of chemical industry. The p-chlorobromobenzene is prepared mainly by heating bromobenzene and iron powder to 80 deg.C, dripping bromine, reacting at 90-100 deg.C for 2.5h, and rectifying or recrystallizing the crude product with ethanol to obtain the final product. However, in the preparation process of the bromochlorobenzene, o-chlorobromobenzene impurities are easily generated, the boiling points of the bromochlorobenzene and the o-chlorobromobenzene are similar, and other physical properties are also similar, so that the bromochlorobenzene and the o-chlorobromobenzene are not easily separated by adopting a rectification or ethanol recrystallization mode, the separation steps are complicated, and the product loss is more. Therefore, the search for a method capable of separating p-bromochloro-benzene from o-bromochloro-benzene and p-bromochloro-benzene isomers has been an important direction for researchers to explore on the premise of ensuring good separation rate and product yield and reducing cost.
Disclosure of Invention
Aiming at the problem that the existing method for separating p-bromochloro-benzene and o-bromochloro-benzene has poor separation effect, the invention provides a method for separating p-bromochloro-benzene and o-bromochloro-benzene by a suspension melting crystallization method.
In order to solve the technical problems, the technical scheme provided by the invention is as follows:
a method for separating p-bromochlorobenzene and o-bromochlorobenzene by a suspension melting crystallization method comprises the following steps:
step one, ultrasonically dispersing a solid-liquid mixture of o-bromochlorobenzene and p-bromochlorobenzene for 25-35min to obtain a dispersion liquid; adding the dispersion liquid into a melt crystallizer, and heating to 60-75 ℃ to obtain mixed molten liquid;
and step two, cooling the mixed molten liquid to-10-20 ℃ at a cooling rate of 0.05-0.5 ℃/min, growing crystals for 1-6h, filtering, washing and drying to obtain the p-chlorobromobenzene.
Compared with the prior art, the method for separating the p-bromochloro-benzene and the o-bromochloro-benzene by using the suspension melting crystallization method provided by the invention realizes separation of the p-bromochloro-benzene and the o-bromochloro-benzene isomers by designing a reasonable crystallization process route and controlling crystallization process conditions, and avoids the problems of serious occlusion of mother liquor and low product purity in the crystallization process of a common melting crystallization method by controlling the cooling rate and the crystal growing temperature. The purity of the p-bromochloro-benzene prepared by the method can reach more than 99 percent, the one-way yield can reach 66.1 percent at most, the crystallization process does not need to be heated and sweated or seed crystal is added, the purity of the p-bromochloro-benzene product can also reach more than 99 percent, the economic benefit is improved, the energy consumption is reduced, the cost is saved, meanwhile, no organic solvent is introduced in the crystallization process, the environmental pollution is small, and the requirements of energy conservation and emission reduction are met. The method for separating the p-bromochlorobenzene and the o-bromochlorobenzene is applied to the purification process of industrially producing the crude p-bromochlorobenzene, can greatly simplify the purification steps, improve the production efficiency, reduce the investment of corresponding equipment and reduce the production cost, does not need to additionally add an organic solvent in the purification process, and has obvious economic benefit and environmental protection benefit.
The melt crystallizer is a container with a jacket and a stirring device, cooling water or ethanol is circulated in the jacket to control the temperature of a crystallization system, the stirring device can enable materials in the crystallization system to be in a suspension state, and large-particle crystals are always in dynamic balance of crushing and generation in the suspension state, so that the collision and crushing probability of the large-particle crystals is high and the large-particle crystals are difficult to stably exist, so that the impurity wrapping amount in the crystals is small, and meanwhile, the stirring can prevent the crystals from caking on the inner wall of the container, the products are difficult to separate, and the problems of excessive product loss are solved.
The melting point of the bromoxybenzene is 68 ℃, theoretically, crystals should begin to precipitate when the temperature of the system is reduced to below 65 ℃, however, in the experimental process, the inventor surprisingly discovers that no bromoxybenzene crystals are precipitated when the temperature of the system is reduced to about 40 ℃, which indicates that the metastable zone of the bromoxybenzene crystals is very wide, so that explosive nucleation is very easy to occur in the experimental process, the crystallization process is out of control, and the problems of fine crystals and poor quality of the prepared product are caused. Therefore, the inventor adopts a suspension crystallization mode to solve the problems by adding an ultrasonic dispersion step before the raw material is put into the crystallizer and controlling a proper cooling rate and a cooling final temperature.
Preferably, the step one further comprises the following steps: regulating the temperature of the mixed molten liquid to 5-10 ℃, and maintaining for 30-60 min.
The mixed molten liquid is adjusted downwards by 5-10 ℃ firstly, and is maintained for 30-60min, which is beneficial to maintaining the stability of the system temperature and the subsequent cooling, so that the system cooling is more uniform, the cooling time is shortened, and the production efficiency is improved.
Preferably, the mass percentage of the p-chlorobromobenzene in the mixed melting liquid is not less than 50%.
The suspension crystallization of the invention leads the crystal to have more ideal growth rate, the ultrasonic is matched with the suspension crystallization, and the proper temperature reduction rate and the crystal growing temperature are controlled, thus avoiding the impurity occlusion problem caused by the burst nucleation problem, and leading the high-purity crystal to be obtained even in the melt liquid with relatively high impurity content. The separation method provided by the invention can separate the crude product of the p-chlorobromobenzene with the p-chlorobromobenzene content higher than 50% and prepare the p-chlorobromobenzene product with the purity higher than 99%.
Preferably, the step two further comprises the following steps before suction filtration: heating the obtained suspension to 0-20 ℃ at the heating rate of 0.05-0.5 ℃/min after finishing the crystal growth, and maintaining for 1-6 h.
More preferably, the heating rate is 0.3 ℃/min, the temperature is raised to 4 ℃, and the holding time is 1.5 h.
The separation method provided by the invention can also comprise a subsequent sweating step to improve the yield of the product, but the subsequent sweating step has no beneficial effect on the improvement of the purity of the bromochlorobenzene product, and the purity of the bromochlorobenzene product is basically the same when the sweating step is increased compared with the non-exertion step.
Preferably, in the second step, the temperature is reduced to-2 ℃ at a rate of 0.2 ℃/min.
Preferably, in the second step, the time for growing the crystals is 4 h.
The optimal cooling rate, cooling final temperature and crystal growing time can ensure that the crystallization process has ideal crystal growth rate, avoid impurity occlusion and are beneficial to improving the purity and yield of products.
In the second step, the stirring speed is controlled to be 160-300r/min in the processes of temperature reduction and crystal growing.
The stirring speed has great influence on the separation and purification effect, and if the stirring speed is too low, the suspension density of crystals is not uniform and channeling phenomenon can occur, so that the product purity is low; the stirring speed is too high, which has little influence on the purity of the product, but can reduce the granularity of crystals and is not beneficial to subsequent filtration and washing.
The method for separating the p-bromochloro-benzene and the o-bromochloro-benzene isomers provided by the invention does not need the steps of repeated temperature reduction and temperature rise and sweating or seed crystal addition, and only needs one temperature reduction process to ensure that the purity of the prepared p-bromochloro-benzene reaches more than 99 percent, greatly simplifies the production process, can obviously improve the production efficiency, and has wide application prospect.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Example 1
A method for separating p-bromochlorobenzene and o-bromochlorobenzene by a suspension melting crystallization method comprises the following steps:
step one, ultrasonically dispersing a solid-liquid mixture of o-bromochlorobenzene and p-bromochlorobenzene with the p-bromochlorobenzene content of 50% for 30min to obtain a dispersion liquid; adding the dispersion liquid into a melt crystallizer, and heating to 60 ℃ to obtain mixed molten liquid;
step two, cooling the mixed molten liquid to 55 ℃, maintaining for 30min, then cooling to-2 ℃ at the cooling rate of 0.2 ℃/min, and growing crystals for 2h to obtain p-chlorobromobenzene crude crystals;
and step three, heating the p-chlorobromobenzene crude crystal to 4 ℃ at the heating rate of 0.3 ℃/min for sweating, maintaining for 1.5 hours to obtain a p-chlorobromobenzene pure crystal, performing suction filtration, washing with water, drying to obtain a p-chlorobromobenzene product, collecting and mixing the discharged crystallization mother liquor, and recycling. The yield of the bromobenzene chloride is 60.6 percent, and the purity is 99.71 percent.
Example 2
A method for separating p-bromochlorobenzene and o-bromochlorobenzene by a suspension melting crystallization method comprises the following steps:
step one, ultrasonically dispersing a solid-liquid mixture of o-bromochlorobenzene and p-bromochlorobenzene with the p-bromochlorobenzene content of 50% for 30min to obtain a dispersion liquid; adding the dispersion liquid into a melt crystallizer, and heating to 60 ℃ to obtain mixed molten liquid;
and step two, cooling the mixed molten liquid to 55 ℃, maintaining for 30min, then cooling to-2 ℃ at the cooling rate of 0.2 ℃/min, growing crystals for 2h, carrying out suction filtration, washing with water, drying to obtain a p-chlorobromobenzene product, and collecting, mixing and recycling the discharged crystallized mother liquid. The yield of the bromobenzene chloride is 66.1 percent, and the purity is 99.54 percent.
Example 3
A method for separating p-bromochlorobenzene and o-bromochlorobenzene by a suspension melting crystallization method comprises the following steps:
step one, ultrasonically dispersing a solid-liquid mixture of o-bromochlorobenzene and p-bromochlorobenzene with the p-bromochlorobenzene content of 50% for 35min to obtain a dispersion liquid; adding the dispersion liquid into a melt crystallizer, and heating to 75 ℃ to obtain mixed molten liquid;
and step two, cooling the mixed molten liquid to-10 ℃ at a cooling rate of 0.5 ℃/min, growing crystals for 6 hours, carrying out suction filtration, washing with water, and drying to obtain a p-chlorobromobenzene product, and collecting and mixing the discharged crystallization mother liquor for recycling. The yield of the bromobenzene chloride is 55.4 percent, and the purity is 99.04 percent.
Example 4
A method for separating p-bromochlorobenzene and o-bromochlorobenzene by a suspension melting crystallization method comprises the following steps:
step one, ultrasonically dispersing a solid-liquid mixture of o-bromochlorobenzene and p-bromochlorobenzene with the p-bromochlorobenzene content of 50% for 25min to obtain a dispersion liquid; adding the dispersion liquid into a melt crystallizer, and heating to 65 ℃ to obtain mixed molten liquid;
and step two, cooling the mixed molten liquid to-5 ℃ at a cooling rate of 0.05 ℃/min, growing crystals for 2 hours, carrying out suction filtration, washing with water, drying to obtain a p-chlorobromobenzene product, and collecting, mixing and recycling discharged crystallization mother liquor. The yield of the bromobenzene chloride is 56.3 percent, and the purity is 99.12 percent.
Example 5
A method for separating p-bromochlorobenzene and o-bromochlorobenzene by a suspension melting crystallization method comprises the following steps:
step one, ultrasonically dispersing a solid-liquid mixture of o-bromochlorobenzene and p-bromochlorobenzene with the content of the p-bromochlorobenzene of 80 percent for 25min to obtain a dispersion liquid; adding the dispersion liquid into a melt crystallizer, and heating to 65 ℃ to obtain mixed molten liquid;
and step two, cooling the mixed molten liquid to 20 ℃ at a cooling rate of 0.15 ℃/min, growing crystals for 1h, carrying out suction filtration, washing with water, and drying to obtain a p-chlorobromobenzene product, and collecting, mixing and recycling the discharged crystallization mother liquor. The yield of the bromobenzene chloride is 58.6 percent, and the purity is 99.08 percent.
Example 6
A method for separating p-bromochlorobenzene and o-bromochlorobenzene by a suspension melting crystallization method comprises the following steps:
step one, ultrasonically dispersing a solid-liquid mixture of o-bromochlorobenzene and p-bromochlorobenzene with the p-bromochlorobenzene content of 50% for 30min to obtain a dispersion liquid; adding the dispersion liquid into a melt crystallizer, and heating to 60 ℃ to obtain mixed molten liquid;
step two, cooling the mixed molten liquid to 55 ℃, maintaining for 30min, then cooling to-6 ℃ at the cooling rate of 0.4 ℃/min, and growing crystals for 2h to obtain p-chlorobromobenzene crude crystals;
and step three, heating the p-chlorobromobenzene crude crystal to 0 ℃ at the heating rate of 0.05 ℃/min, sweating, maintaining for 6 hours to obtain a p-chlorobromobenzene pure crystal, carrying out suction filtration, washing with water, drying to obtain a p-chlorobromobenzene product, collecting and mixing the discharged crystallization mother liquor, and recycling. The yield of the bromobenzene chloride is 60.3 percent, and the purity is 99.68 percent.
Example 7
A method for separating p-bromochlorobenzene and o-bromochlorobenzene by a suspension melting crystallization method comprises the following steps:
step one, ultrasonically dispersing a solid-liquid mixture of o-bromochlorobenzene and p-bromochlorobenzene with the p-bromochlorobenzene content of 50% for 30min to obtain a dispersion liquid; adding the dispersion liquid into a melt crystallizer, and heating to 75 ℃ to obtain mixed molten liquid;
step two, cooling the mixed molten liquid to 65 ℃, maintaining for 30min, then cooling to 6 ℃ at a cooling rate of 0.3 ℃/min, and growing crystals for 3h to obtain p-chlorobromobenzene crude crystals;
and step three, heating the p-chlorobromobenzene crude crystal to 20 ℃ at the heating rate of 0.5 ℃/min, sweating, maintaining for 3 hours to obtain a p-chlorobromobenzene pure crystal, carrying out suction filtration, washing with water, drying to obtain a p-chlorobromobenzene product, collecting and mixing the discharged crystallization mother liquor, and recycling. The yield of the bromobenzene chloride is 58.3 percent, and the purity is 99.47 percent.
Comparative example 1
A method for separating p-bromochlorobenzene and o-bromochlorobenzene by a suspension melting crystallization method comprises the following steps:
step one, adding a solid-liquid mixture of o-bromochlorobenzene and p-bromochlorobenzene with the p-bromochlorobenzene content of 50% into a melting crystallizer, and heating to 60 ℃ to obtain a mixed molten liquid;
step two, cooling the mixed molten liquid to 55 ℃, maintaining for 30min, then cooling to-2 ℃ at the cooling rate of 0.2 ℃/min, and growing crystals for 2h to obtain p-chlorobromobenzene crude crystals;
and step three, heating the p-chlorobromobenzene crude crystal to 4 ℃ at the heating rate of 0.3 ℃/min for sweating, maintaining for 1.5 hours to obtain a p-chlorobromobenzene pure crystal, performing suction filtration, washing with water, drying to obtain a p-chlorobromobenzene product, collecting and mixing the discharged crystallization mother liquor, and recycling. The yield of the bromobenzene chloride is 50.2 percent, and the purity is 97.2 percent.
Comparative example 2
A method for separating p-bromochlorobenzene and o-bromochlorobenzene by a suspension melting crystallization method comprises the following steps:
step one, acoustically dispersing a solid-liquid mixture of o-bromochlorobenzene and p-bromochlorobenzene with the p-bromochlorobenzene content of 50% for 30min to obtain a dispersion liquid; adding the dispersion liquid into a melt crystallizer, and heating to 60 ℃ to obtain mixed molten liquid;
step two, cooling the mixed molten liquid to 55 ℃, maintaining for 30min, then cooling to-2 ℃ at the cooling rate of 1.0 ℃/min, and growing crystals for 2h to obtain p-chlorobromobenzene crude crystals;
and step three, heating the p-chlorobromobenzene crude crystal to 4 ℃ at the heating rate of 0.8 ℃/min for sweating, maintaining for 1.5 hours to obtain a p-chlorobromobenzene pure crystal, performing suction filtration, washing with water, drying to obtain a p-chlorobromobenzene product, collecting and mixing the discharged crystallization mother liquor, and recycling. The yield of the bromobenzene chloride is 55.6 percent, and the purity is 98.1 percent.
Comparative example 3
A method for separating p-bromochlorobenzene and o-bromochlorobenzene by a suspension melting crystallization method comprises the following steps:
step one, ultrasonically dispersing a solid-liquid mixture of o-bromochlorobenzene and p-bromochlorobenzene with the p-bromochlorobenzene content of 50% for 30min to obtain a dispersion liquid; adding the dispersion liquid into a melt crystallizer, and heating to 60 ℃ to obtain mixed molten liquid;
step two, cooling the mixed molten liquid to 55 ℃, maintaining for 30min, then cooling to 25 ℃ at the cooling rate of 0.2 ℃/min, and growing crystals for 2h to obtain p-chlorobromobenzene crude crystals;
and step three, heating the p-chlorobromobenzene crude crystal to 35 ℃ at the heating rate of 0.3 ℃/min, sweating, maintaining for 1.5 hours to obtain a p-chlorobromobenzene pure crystal, performing suction filtration, washing with water, drying to obtain a p-chlorobromobenzene product, collecting and mixing the discharged crystallization mother liquor, and recycling. The yield of the bromobenzene chloride is 47.6 percent, and the purity is 96.5 percent.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents or improvements made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (7)
1. A method for separating p-bromochlorobenzene and o-bromochlorobenzene by a suspension melting crystallization method is characterized by comprising the following steps:
step one, ultrasonically dispersing a solid-liquid mixture of o-bromochlorobenzene and p-bromochlorobenzene for 25-35min to obtain a dispersion liquid; adding the dispersion liquid into a melt crystallizer, and heating to 60-75 ℃ to obtain mixed molten liquid; the mass percentage content of the p-chlorobromobenzene in the mixed molten liquid is not lower than 50%;
and step two, cooling the mixed molten liquid to-10-20 ℃ at a cooling rate of 0.05-0.5 ℃/min, growing crystals for 1-6h, filtering, washing and drying to obtain the p-chlorobromobenzene.
2. The method for separating p-bromochlorobenzene and o-bromochlorobenzene by suspension melt crystallization according to claim 1, wherein the step one further comprises the steps of: regulating the temperature of the mixed molten liquid to 5-10 ℃, and maintaining for 30-60 min.
3. The method for separating p-bromochlorobenzene and o-bromochlorobenzene by suspension melt crystallization according to claim 1 or 2, further comprising the following steps before the suction filtration in the second step: heating the obtained suspension to 0-20 ℃ at the heating rate of 0.05-0.5 ℃/min after finishing the crystal growth, and maintaining for 1-6 h.
4. The method for separating p-bromochlorobenzene from o-bromochlorobenzene according to claim 3, wherein the temperature rise rate is 0.3 ℃/min, the temperature rise to 4 ℃ and the holding time is 1.5 h.
5. The method for separating p-bromochlorobenzene and o-bromochlorobenzene by suspension melting crystallization according to claim 1, wherein in the second step, the temperature reduction rate is 0.2 ℃/min, and the temperature is reduced to-2 ℃.
6. The method for separating p-bromochlorobenzene and o-bromochlorobenzene by suspension melt crystallization according to claim 1 or 5, wherein in the second step, the crystal growth time is 4 h.
7. The method for separating p-bromochlorobenzene and o-bromochlorobenzene by suspension melting crystallization according to claim 1, wherein in the second step, the stirring rate is controlled to be 160-300r/min during the cooling and crystal growth process.
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