CN113277926B - Method for separating high-purity isomers of tetramethyl biphenyl by rectification-melt crystallization coupling - Google Patents
Method for separating high-purity isomers of tetramethyl biphenyl by rectification-melt crystallization coupling Download PDFInfo
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- 238000002425 crystallisation Methods 0.000 title claims abstract description 42
- 230000008025 crystallization Effects 0.000 title claims abstract description 42
- 238000000034 method Methods 0.000 title claims abstract description 37
- WBODDOZXDKQEFS-UHFFFAOYSA-N 1,2,3,4-tetramethyl-5-phenylbenzene Chemical class CC1=C(C)C(C)=CC(C=2C=CC=CC=2)=C1C WBODDOZXDKQEFS-UHFFFAOYSA-N 0.000 title claims abstract description 31
- 230000008878 coupling Effects 0.000 title claims abstract description 12
- 238000010168 coupling process Methods 0.000 title claims abstract description 12
- 238000005859 coupling reaction Methods 0.000 title claims abstract description 12
- NGDMCVXWKKYGRQ-UHFFFAOYSA-N 1-(2,3-dimethylphenyl)-2,3-dimethylbenzene Chemical group CC1=CC=CC(C=2C(=C(C)C=CC=2)C)=C1C NGDMCVXWKKYGRQ-UHFFFAOYSA-N 0.000 claims abstract description 35
- 238000002844 melting Methods 0.000 claims abstract description 35
- 239000013078 crystal Substances 0.000 claims abstract description 33
- LRSDMTARWGKQDI-UHFFFAOYSA-N 1-(3,4-dimethylphenyl)-2,3-dimethylbenzene Chemical group C1=C(C)C(C)=CC=C1C1=CC=CC(C)=C1C LRSDMTARWGKQDI-UHFFFAOYSA-N 0.000 claims abstract description 30
- YXBIAYXZUDJVEB-UHFFFAOYSA-N 4-(3,4-dimethylphenyl)-1,2-dimethylbenzene Chemical group C1=C(C)C(C)=CC=C1C1=CC=C(C)C(C)=C1 YXBIAYXZUDJVEB-UHFFFAOYSA-N 0.000 claims abstract description 28
- 238000000926 separation method Methods 0.000 claims abstract description 15
- 239000000203 mixture Substances 0.000 claims abstract description 14
- 230000035900 sweating Effects 0.000 claims description 49
- 238000001816 cooling Methods 0.000 claims description 35
- 230000008018 melting Effects 0.000 claims description 30
- 238000010438 heat treatment Methods 0.000 claims description 28
- 239000012452 mother liquor Substances 0.000 claims description 27
- 210000004243 sweat Anatomy 0.000 claims description 25
- 238000007599 discharging Methods 0.000 claims description 17
- 239000000463 material Substances 0.000 claims description 14
- 239000000155 melt Substances 0.000 claims description 7
- 239000000725 suspension Substances 0.000 claims description 7
- 239000007788 liquid Substances 0.000 claims description 5
- 239000011552 falling film Substances 0.000 claims description 3
- 239000010413 mother solution Substances 0.000 claims description 3
- 238000005265 energy consumption Methods 0.000 abstract description 3
- 238000004519 manufacturing process Methods 0.000 abstract description 3
- ZUOUZKKEUPVFJK-UHFFFAOYSA-N diphenyl Chemical compound C1=CC=CC=C1C1=CC=CC=C1 ZUOUZKKEUPVFJK-UHFFFAOYSA-N 0.000 description 10
- 230000005496 eutectics Effects 0.000 description 6
- 235000010290 biphenyl Nutrition 0.000 description 5
- 239000004305 biphenyl Substances 0.000 description 5
- 230000003647 oxidation Effects 0.000 description 5
- 238000007254 oxidation reaction Methods 0.000 description 5
- GTDPSWPPOUPBNX-UHFFFAOYSA-N ac1mqpva Chemical compound CC12C(=O)OC(=O)C1(C)C1(C)C2(C)C(=O)OC1=O GTDPSWPPOUPBNX-UHFFFAOYSA-N 0.000 description 4
- WKDNYTOXBCRNPV-UHFFFAOYSA-N bpda Chemical compound C1=C2C(=O)OC(=O)C2=CC(C=2C=C3C(=O)OC(C3=CC=2)=O)=C1 WKDNYTOXBCRNPV-UHFFFAOYSA-N 0.000 description 4
- 239000007791 liquid phase Substances 0.000 description 4
- 230000000630 rising effect Effects 0.000 description 4
- 239000002994 raw material Substances 0.000 description 3
- VACCAVUAMIDAGB-UHFFFAOYSA-N sulfamethizole Chemical compound S1C(C)=NN=C1NS(=O)(=O)C1=CC=C(N)C=C1 VACCAVUAMIDAGB-UHFFFAOYSA-N 0.000 description 3
- 238000005406 washing Methods 0.000 description 3
- JVERADGGGBYHNP-UHFFFAOYSA-N 5-phenylbenzene-1,2,3,4-tetracarboxylic acid Chemical compound OC(=O)C1=C(C(O)=O)C(C(=O)O)=CC(C=2C=CC=CC=2)=C1C(O)=O JVERADGGGBYHNP-UHFFFAOYSA-N 0.000 description 2
- CTQNGGLPUBDAKN-UHFFFAOYSA-N O-Xylene Chemical group CC1=CC=CC=C1C CTQNGGLPUBDAKN-UHFFFAOYSA-N 0.000 description 2
- 239000004642 Polyimide Substances 0.000 description 2
- 229920001721 polyimide Polymers 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- UERPUZBSSSAZJE-UHFFFAOYSA-N 3-chlorophthalic anhydride Chemical compound ClC1=CC=CC2=C1C(=O)OC2=O UERPUZBSSSAZJE-UHFFFAOYSA-N 0.000 description 1
- FYYYKXFEKMGYLZ-UHFFFAOYSA-N 4-(1,3-dioxo-2-benzofuran-5-yl)-2-benzofuran-1,3-dione Chemical compound C=1C=C2C(=O)OC(=O)C2=CC=1C1=CC=CC2=C1C(=O)OC2=O FYYYKXFEKMGYLZ-UHFFFAOYSA-N 0.000 description 1
- 238000011001 backwashing Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000000151 deposition Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000001125 extrusion Methods 0.000 description 1
- 238000011031 large-scale manufacturing process Methods 0.000 description 1
- 239000000178 monomer Substances 0.000 description 1
- 229940078552 o-xylene Drugs 0.000 description 1
- 238000005691 oxidative coupling reaction Methods 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- XNGIFLGASWRNHJ-UHFFFAOYSA-L phthalate(2-) Chemical compound [O-]C(=O)C1=CC=CC=C1C([O-])=O XNGIFLGASWRNHJ-UHFFFAOYSA-L 0.000 description 1
- 239000002243 precursor Substances 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 238000007790 scraping Methods 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C7/00—Purification; Separation; Use of additives
- C07C7/005—Processes comprising at least two steps in series
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C7/00—Purification; Separation; Use of additives
- C07C7/04—Purification; Separation; Use of additives by distillation
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C7/00—Purification; Separation; Use of additives
- C07C7/14—Purification; Separation; Use of additives by crystallisation; Purification or separation of the crystals
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Abstract
The invention relates to the field of organic chemistry, and discloses a method for separating a high-purity tetramethylbiphenyl isomer by rectification-melt crystallization coupling, which comprises the following steps: (1) roughly dividing: enriching three isomers in a tetramethylbiphenyl isomer mixture by adopting a rectification or crystallization mode to obtain 2,2 ', 3, 3' -tetramethylbiphenyl, 2,3 ', 3, 4' -tetramethylbiphenyl and 3,3 ', 4, 4' -tetramethylbiphenyl with single isomer purity of 70-90%; (2) finely dividing: respectively carrying out melt crystallization on the single isomers obtained in the step (1) to obtain high-purity crystals with the purity of more than 99.5%. The invention purifies the tetramethyl biphenyl isomer by adopting a rectification-melting crystallization coupling separation method, can enable the single isomer to reach the ultrahigh purity of 99.9999 percent, has low energy consumption, simplified equipment, high production efficiency and no three wastes, and is an environment-friendly green process.
Description
Technical Field
The invention relates to the field of organic chemistry, in particular to a method for separating a high-purity tetramethylbiphenyl isomer by rectification-melt crystallization coupling.
Background
Tetramethyl biphenyl is an important precursor compound for preparing biphenyl tetracid dianhydride (BPDA for short).
Biphenyltetracarboxylic dianhydride is an important polyimide monomer and plays an important role in the polyimide material industry. The biphenyl tetracid dianhydride has three isomers, namely symmetrical s-BPDA, i-BPDA and asymmetrical a-BPDA. The biphenyl tetracid dianhydride is prepared by a plurality of methods, including a chlorophthalic anhydride coupling route, a phthalate coupling route, a liquid phase oxidation route and the like. Of these, the first two routes have been commercialized, but have limited applications due to high raw material cost and high catalyst cost.
The liquid-phase oxidation route using tetramethyl biphenyl as a raw material is a simpler and more economical preparation route which can replace the prior production technology. Mitsubishi chemical corporation of Japan developed a method for preparing tetramethylbiphenyl by oxidative coupling of o-xylene and then preparing biphenyltetracarboxylic acid by oxidation. The Chinese patents CN200410089450.9, CN200810142756.4, CN201310049837.0, CN201310050630.5 and ZL202010222907.8 all report the preparation method of tetramethyl biphenyl.
Chinese patent CN201410476886.7 reports a method for separating tetramethylbiphenyl into a single isomer with purity of 90% -99.5% by rectification, but the separation process has problems of high energy consumption and low efficiency, and it is difficult to obtain a single isomer with higher purity. And the high-purity single tetramethyl biphenyl isomer is the basis for preparing the high-purity BPDA by a liquid-phase oxidation method.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides a method for separating a high-purity tetramethylbiphenyl isomer by rectification-melt crystallization coupling, which comprises the following steps:
(1) roughly dividing: the tetramethylbiphenyl isomer mixture comprises three isomers which are 2,2 ', 3, 3' -tetramethylbiphenyl, 2,3 ', 3, 4' -tetramethylbiphenyl and 3,3 ', 4, 4' -tetramethylbiphenyl respectively; when the percentage of 2,2 ', 3, 3' -tetramethyl biphenyl in the total mass of the three isomers is less than 15%, enriching the three isomers of the tetramethyl biphenyl isomer mixture by adopting a rectification mode to obtain 2,2 ', 3, 3' -tetramethyl biphenyl, 2,3 ', 3, 4' -tetramethyl biphenyl and 3,3 ', 4, 4' -tetramethyl biphenyl with single isomer purity of 70-90%; when the 2,2 ', 3, 3' -tetramethyl biphenyl accounts for more than or equal to 15 percent of the total mass of the three isomers, 2 ', 3, 3' -tetramethyl biphenyl, 2,3 ', 3, 4' -tetramethyl biphenyl and 3,3 ', 4, 4' -tetramethyl biphenyl with single isomer purity of 70-90 percent are obtained by adopting a rectification or crystallization mode;
(2) finely dividing: respectively carrying out melt crystallization on the 2,2 ', 3, 3' -tetramethylbiphenyl, the 2,3 ', 3, 4' -tetramethylbiphenyl and the 3,3 ', 4, 4' -tetramethylbiphenyl with the single isomer purity of 70-90% obtained in the step (1) to obtain high-purity crystals, taking the crystals with the purity of more than 99.5% as qualified products to enter a product tank, and repeating the step (2) when the purity of 70-99.5% is obtained; and (3) repeating the step (1) for crude separation if the purity is lower than 70%.
The above technical solution can be further optimized as follows:
the process flow for obtaining the 2,2 ', 3, 3' -tetramethyl biphenyl with the purity of 70% -90% in the step (1) by a crystallization mode is as follows: heating the tetramethyl biphenyl isomer mixture to 125 ℃ for melting, adding the mixture into a suspension melting crystallizer, cooling to 75 ℃ at a cooling rate of 0.5 ℃/min, keeping the temperature for 0.5h, and carrying out solid-liquid separation.
The process flow for obtaining the 2,2 ', 3, 3' -tetramethyl biphenyl with the purity of more than 99.5% by the step (2) through a melt crystallization procedure is as follows: heating the material to 125 ℃ for melting, adding the material into a box-type melting crystallizer, cooling to 115-fold sand-heat 120 ℃ at the speed of 0.15-0.25 ℃/min, then cooling to 105-fold sand-heat 108 ℃ at the speed of 0.1-0.12 ℃/min, keeping the temperature for 1h, and discharging the mother solution; crystal sweating, wherein the sweating temperature rise rate is 0.075-0.1 ℃/min, the sweating final temperature is 125 ℃, and sweat is discharged; and heating to melt the crystals and collect the product.
The process flow for obtaining the 2,3 ', 3, 4' -tetramethyl biphenyl with the purity of more than 99.5% by the step (2) through a melt crystallization procedure is as follows: heating the material to 45 ℃ for melting, adding the material into a box-type melting crystallizer, cooling to 35-38 ℃ at the speed of 0.14-0.2 ℃/min, then cooling to 30-32 ℃ at the speed of 0.08-0.1 ℃/min, keeping the temperature for 2.5-4h, and discharging mother liquor; crystal sweating, wherein the sweating temperature rise rate is 0.05-0.06 ℃/min, the sweating final temperature is 45 ℃, and sweat is discharged; and heating to melt the crystals and collect the product.
The process flow for obtaining the 3,3 ', 4, 4' -tetramethyl biphenyl with the purity of more than 99.5% by the step (2) through a melt crystallization procedure is as follows: heating the material to 75 ℃ for melting, adding the material into a box-type melting crystallizer, cooling to 64-68 ℃ at the speed of 0.12-0.2 ℃/min, then cooling to 58-60 ℃ at the speed of 0.08-0.1 ℃/min, keeping the temperature for 1.5-2h, and discharging mother liquor; crystal sweating, wherein the sweating temperature rise rate is 0.07-0.08 ℃/min, the sweating final temperature is 75 ℃, and sweat is discharged; and heating to melt the crystals and collect the product.
The mass ratio of the 2,2 ', 3, 3' -tetramethylbiphenyl, the 2,3 ', 3, 4' -tetramethylbiphenyl and the 3,3 ', 4, 4' -tetramethylbiphenyl in the tetramethylbiphenyl isomer mixture in the step (1) is any ratio.
And the mother solution and the sweat are subjected to a melting crystallization procedure.
And (3) melting and crystallizing the qualified product with the purity of more than 99.5% in the step (2) again to obtain a high-quality product with the purity of 99.9999%.
The remelting crystallization adopts a falling film crystallizer or a suspension crystallizer.
Compared with the prior art, the invention mainly has the following beneficial technical effects:
1. the invention separates out high-purity single tetramethyl biphenyl isomer from tetramethyl biphenyl isomer mixture by adopting a rectification-melting crystallization coupling separation method, and the method is suitable for tetramethyl biphenyl isomer mixed raw materials with any proportion.
2. The rectification only needs to enrich the single isomer to the mass percentage content of 70-90 percent, thereby greatly reducing the rectification energy consumption, simplifying the equipment rectification, having low operation cost and high production efficiency.
3. Through a melting crystallization procedure, the purity of the single isomer is further improved to more than 99.5 percent and even to ultra-high purity of 99.9999 percent.
4. No additional solvent is needed, the operation condition is mild, no three wastes are generated, the recovery rate is 100 percent, and the method is an environment-friendly green process and is suitable for industrial large-scale production.
5. The high-purity separation of the single tetramethyl biphenyl isomer solves the problem of the separation of the BPDA isomer, and lays a good foundation for preparing the high-purity BPDA isomer by liquid-phase oxidation.
Detailed Description
The process of the invention is further illustrated by the following examples, but is not limited thereto.
Example 1
1kg of tetramethylbiphenyl isomer mixture, wherein the mass ratio of the three isomers is 2,2 ', 3, 3' -tetramethylbiphenyl: 2,3 ', 3, 4' -tetramethylbiphenyl: 3,3 ', 4, 4' -tetramethylbiphenyl =4:3: 3. The separation is carried out by the following steps:
1. heating the mixed isomer to 125 ℃ for melting, adding the mixed isomer into a suspension melting crystallizer, cooling to 75 ℃ at a cooling rate of 0.5 ℃/min, keeping the temperature for 0.5h, carrying out solid-liquid separation, and discharging mother liquor to obtain 362g of 2,2 ', 3, 3' -tetramethyl biphenyl with the purity of 89%; heating 362g of 2,2 ', 3, 3' -tetramethyl biphenyl to 125 ℃ for melting, adding the melted biphenyl into a box-type melting crystallizer, cooling to 115 ℃ at the speed of 0.2 ℃/min, then cooling to 108 ℃ at the speed of 0.1 ℃/min, keeping the temperature for 1h, and discharging mother liquor; sweating the crystal, wherein the sweating temperature rise rate is 0.08 ℃/min, the sweating final temperature is 125 ℃, and sweat is discharged; and heating to melt the crystals and collect the product. Under the condition of mechanically applying sweat for crystallization, 270g of 2,2 ', 3, 3' -tetramethyl biphenyl with the mass percentage of 99.8 percent can be prepared.
2. And combining the mother liquor of the suspension melt crystallizer and the mother liquor of the box-type melt crystallizer, and roughly separating by rectification to obtain 84.6 mass percent of 2,2 ', 3, 3' -tetramethyl biphenyl 130g, 79.5 mass percent of 2,3 ', 3, 4' -tetramethyl biphenyl 280g and 82 mass percent of 3,3 ', 4, 4' -tetramethyl biphenyl 320g in sequence.
3. 2,2 ', 3, 3' -tetramethyl biphenyl with mass percent of 84.6 percent enters a box-type melting crystallizer, and through the melting-crystallization-sweating steps, 88g of 2,2 ', 3, 3' -tetramethyl biphenyl with mass percent of 99.8 percent is obtained under the condition of mechanically applying sweat for crystallization.
Adding 280g of 79.5 mass percent of 2,3 ', 3, 4' -tetramethyl biphenyl into a box-type melt crystallizer, cooling to 35 ℃ from 45 ℃ at the speed of 0.2 ℃/min, then cooling to 32 ℃ at the speed of 0.1 ℃/min, keeping the temperature for 3h, and discharging mother liquor for sweating; the sweating temperature rising rate is 0.05 ℃/min, the sweating final temperature is 45 ℃, and sweat is discharged; and heating to melt the crystals and collect the product. When sweat is mechanically applied and crystallized, 178g of 2,3 ', 3, 4' -tetramethyl biphenyl with the mass percentage of 99.9 percent can be prepared.
Adding 320g of 82 mass percent of 3,3 ', 4, 4' -tetramethyl biphenyl into a box-type melt crystallizer, cooling to 66 ℃ from 75 ℃ at the speed of 0.2 ℃/min, then cooling to 58 ℃ at the speed of 0.1 ℃/min, keeping the temperature for 2h, and discharging mother liquor for sweating; the sweating temperature rising rate is 0.07 ℃/min, the sweating final temperature is 75 ℃, and sweat is discharged; and heating to melt the crystals and collect the product. Under the condition of mechanically applying sweat for crystallization, 210g of 3,3 ', 4, 4' -tetramethyl biphenyl with the mass percentage of 99.8 percent can be prepared.
4. And 3, repeating the rectification-melting crystallization steps of the eutectic mother liquor with the mass percentage of less than 70% in the step 3 until the eutectic mother liquor is completely separated. Finally, 400g of 2,2 ', 3, 3' -tetramethylbiphenyl with a purity of 99.7%, 300g of 2,3 ', 3, 4' -tetramethylbiphenyl with a purity of 99.9%, and 300g of 3,3 ', 4, 4' -tetramethylbiphenyl with a purity of 99.8% were obtained.
Example 2
3kg of tetramethylbiphenyl isomer mixture, wherein the mass ratio of the three isomers is 2,2 ', 3, 3' -tetramethylbiphenyl: 2,3 ', 3, 4' -tetramethylbiphenyl: 3,3 ', 4, 4' -tetramethylbiphenyl =12:65: 23. The separation is carried out by the following steps:
1. the mixed isomers are roughly separated by rectification, and 345g of 2,2 ', 3, 3' -tetramethyl biphenyl with the mass percent of 88%, 2120g of 2,3 ', 3, 4' -tetramethyl biphenyl with the mass percent of 87.6% and 535g of 3,3 ', 4, 4' -tetramethyl biphenyl with the mass percent of 87% are sequentially obtained.
2. Heating 345g of 88 mass percent of 2,2 ', 3, 3' -tetramethyl biphenyl to 125 ℃ for melting, adding the melted 2,2 ', 3, 3' -tetramethyl biphenyl into a box-type melting crystallizer, cooling to 118 ℃ at the speed of 0.15 ℃/min, then cooling to 108 ℃ at the speed of 0.1 ℃/min, keeping the temperature for 1h, and discharging mother liquor; sweating, wherein the sweating temperature rise rate is 0.075 ℃/min, the sweating final temperature is 125 ℃, and sweat is discharged; and heating to melt the crystals and collect the product. When the sweating mother liquor is mechanically used for crystallization, 258g of 2,2 ', 3, 3' -tetramethyl biphenyl with the mass percentage of 99.9 percent can be prepared.
Adding 2120g of 2,3 ', 3, 4' -tetramethyl biphenyl with the mass percentage of 87.6% into a box-type melt crystallizer, cooling to 38 ℃ from 45 ℃ at the speed of 0.16 ℃/min, then cooling to 30 ℃ at the speed of 0.1 ℃/min, keeping the temperature for 2.5h, and discharging mother liquor for sweating; the sweating temperature-rising rate is 0.06 ℃/min, the sweating final temperature is 45 ℃, and sweat is discharged; and heating to melt the crystals and collect the product. 1522g of 2,3 ', 3, 4' -tetramethylbiphenyl of 99.9% by mass can be prepared in the case of mechanically applying the sweating mother liquor for crystallization.
Adding 535g of 3,3 ', 4, 4' -tetramethyl biphenyl with the mass percent of 87% into a box-type melt crystallizer, cooling to 68 ℃ from 75 ℃ at the speed of 0.18 ℃/min, then cooling to 60 ℃ at the speed of 0.1 ℃/min, keeping the temperature for 1.5h, and discharging mother liquor for sweating; sweating temperature-rising rate is 0.08 ℃/min, the sweating final temperature is 75 ℃, and sweat is discharged; and heating to melt the crystals and collect the product. When the sweating mother liquor is mechanically used for crystallization, 377g of 3,3 ', 4, 4' -tetramethyl biphenyl with the mass percentage of 99.9 percent can be prepared.
3. And (3) repeating the rectification-melting crystallization step on the eutectic point mother liquor with the mass percentage of less than 70% in the step 2 until the eutectic point mother liquor is completely separated. Finally, 360g of 2,2 ', 3, 3' -tetramethylbiphenyl having a purity of 99.9%, 1950g of 2,3 ', 3, 4' -tetramethylbiphenyl having a purity of 99.9%, and 690g of 3,3 ', 4, 4' -tetramethylbiphenyl having a purity of 99.9% were obtained.
Example 3
5kg of tetramethylbiphenyl isomer mixture, wherein the mass ratio of the three isomers is 2,2 ', 3, 3' -tetramethylbiphenyl: 2,3 ', 3, 4' -tetramethylbiphenyl: 3,3 ', 4, 4' -tetramethylbiphenyl =5:35: 60. The separation is carried out by the following steps:
1. the mixed isomers are roughly separated by rectification, and then 330g of 2,2 ', 3, 3' -tetramethyl biphenyl with the mass percentage of 76%, 1447g of 2,3 ', 3, 4' -tetramethyl biphenyl with the mass percentage of 82% and 3223g of 3,3 ', 4, 4' -tetramethyl biphenyl with the mass percentage of 85% are obtained in sequence.
2. Heating 330g of 76 mass percent 2,2 ', 3, 3' -tetramethyl biphenyl to 125 ℃ for melting, adding the melted biphenyl into a box-type melting crystallizer, cooling to 120 ℃ at the speed of 0.25 ℃/min, then cooling to 105 ℃ at the speed of 0.12 ℃/min, keeping the temperature for 1h, and discharging mother liquor for sweating; the sweating temperature-rising rate is 0.1 ℃/min, the sweating final temperature is 125 ℃, and sweat is discharged; and heating to melt the crystals and collect the product. 188g of 2,2 ', 3, 3' -tetramethyl biphenyl with the mass percentage of 99.9 percent can be prepared under the condition of mechanically applying sweat for crystallization.
1447g of 82 mass percent 2,3 ', 3, 4' -tetramethyl biphenyl is added into a box-type melt crystallizer, the temperature is reduced to 36 ℃ from 45 ℃ at the speed of 0.14 ℃/min, then the temperature is reduced to 32 ℃ at the speed of 0.08 ℃/min, the temperature is kept for 4 hours, and mother liquor is discharged for sweating; the sweating temperature rising rate is 0.05 ℃/min, the sweating final temperature is 45 ℃, and sweat is discharged; and heating to melt the crystals and collect the product. When sweat is mechanically applied and crystallized, 913g of 2,3 ', 3, 4' -tetramethylbiphenyl with a mass percentage of 99.9% can be prepared.
3223g of 85 mass percent of 3,3 ', 4, 4' -tetramethyl biphenyl is added into a box-type melt crystallizer, the temperature is reduced to 64 ℃ from 75 ℃ at the speed of 0.12 ℃/min, then the temperature is reduced to 60 ℃ at the speed of 0.08 ℃/min, the temperature is kept for 1.5h, and mother liquor is discharged for sweating; the sweating temperature rising rate is 0.07 ℃/min, the sweating final temperature is 75 ℃, and sweat is discharged; and heating to melt the crystals and collect the product. 2082g of 3,3 ', 4, 4' -tetramethylbiphenyl with the mass percentage of 99.9 percent can be prepared under the condition of mechanically applying sweat for crystallization.
3. And (3) repeating the rectification-melting crystallization step on the eutectic point mother liquor with the mass percentage of less than 70% in the step 2 until the eutectic point mother liquor is completely separated. Finally, 250g of 2,2 ', 3, 3' -tetramethylbiphenyl with the purity of 99.9%, 1750g of 2,3 ', 3, 4' -tetramethylbiphenyl with the purity of 99.9% and 3000g of 3,3 ', 4, 4' -tetramethylbiphenyl with the purity of 99.9% are obtained.
Example 4
Melting 1000g of 2,3 ', 3, 4' -tetramethyl biphenyl with the purity of 99.6%, adding the melted 2,3 ', 3, 4' -tetramethyl biphenyl into a falling film crystallizer, cooling from 46 ℃ to 44.8 ℃ at the speed of 0.01-0.03 ℃/min, keeping the temperature for 0.5h, and discharging mother liquor; then raising the temperature to 45.3 ℃ at the speed of 0.01-0.02 ℃/min for sweating, and discharging sweat; and heating to melt the crystals and collect the product. 280g of 2,3 ', 3, 4' -tetramethyl biphenyl with the mass percentage of 99.9999 percent can be prepared.
Example 5
The method comprises the steps of continuously adding molten 3,3 ', 4, 4' -tetramethyl biphenyl with the purity of 85% into a suspension melting crystallizer, growing crystals to form high-purity product crystal particles under a cooling condition, scraping the inner wall of the crystallizer by a scraper to prevent the crystals from depositing on a cooling surface, feeding solid-liquid mixed crystal slurry into a washing tower, completing solid-liquid separation and solid surface washing in the washing tower, obtaining 3,3 ', 4, 4' -tetramethyl biphenyl with the mass percentage content of more than 99.99% through continuous extrusion and crystal surface backwashing, and continuously feeding and discharging materials in the process.
Claims (4)
1. The method for separating the high-purity isomers of the tetramethylbiphenyl by rectification-melt crystallization coupling is characterized by comprising the following steps of:
(1) roughly dividing: the tetramethylbiphenyl isomer mixture comprises three isomers which are 2,2 ', 3, 3' -tetramethylbiphenyl, 2,3 ', 3, 4' -tetramethylbiphenyl and 3,3 ', 4, 4' -tetramethylbiphenyl respectively; when the percentage of 2,2 ', 3, 3' -tetramethyl biphenyl in the total mass of the three isomers is less than 15%, enriching the three isomers of the tetramethyl biphenyl isomer mixture by adopting a rectification mode to obtain 2,2 ', 3, 3' -tetramethyl biphenyl, 2,3 ', 3, 4' -tetramethyl biphenyl and 3,3 ', 4, 4' -tetramethyl biphenyl with single isomer purity of 70-90%; when the 2,2 ', 3, 3' -tetramethyl biphenyl accounts for more than or equal to 15 percent of the total mass of the three isomers, 2 ', 3, 3' -tetramethyl biphenyl, 2,3 ', 3, 4' -tetramethyl biphenyl and 3,3 ', 4, 4' -tetramethyl biphenyl with single isomer purity of 70-90 percent are obtained by adopting a rectification or crystallization mode;
the process flow for obtaining the 2,2 ', 3, 3' -tetramethyl biphenyl with the purity of 70-90% by a crystallization mode is as follows: heating the tetramethyl biphenyl isomer mixture to 125 ℃ for melting, adding the mixture into a suspension melting crystallizer, cooling to 75 ℃ at a cooling rate of 0.5 ℃/min, keeping the temperature for 0.5h, and performing solid-liquid separation;
(2) finely dividing: respectively carrying out melt crystallization on the 2,2 ', 3, 3' -tetramethylbiphenyl, the 2,3 ', 3, 4' -tetramethylbiphenyl and the 3,3 ', 4, 4' -tetramethylbiphenyl with the single isomer purity of 70-90% obtained in the step (1) to obtain high-purity crystals, taking the crystals with the purity of more than 99.5% as qualified products to enter a product tank, and repeating the step (2) when the purity of 70-99.5% is obtained; repeating the step (1) for coarse separation when the purity is lower than 70%;
the process flow for obtaining the 2,2 ', 3, 3' -tetramethyl biphenyl with the purity of more than 99.5 percent through a melt crystallization procedure is as follows: heating the material to 125 ℃ for melting, adding the material into a box-type melting crystallizer, cooling to 115-fold sand-heat 120 ℃ at the speed of 0.15-0.25 ℃/min, then cooling to 105-fold sand-heat 108 ℃ at the speed of 0.1-0.12 ℃/min, keeping the temperature for 1h, and discharging the mother solution; crystal sweating, wherein the sweating temperature rise rate is 0.075-0.1 ℃/min, the sweating final temperature is 125 ℃, and sweat is discharged; heating to melt the crystals and collecting the product;
the process flow for obtaining the 2,3 ', 3, 4' -tetramethyl biphenyl with the purity of more than 99.5 percent through a melt crystallization procedure is as follows: heating the material to 45 ℃ for melting, adding the material into a box-type melting crystallizer, cooling to 35-38 ℃ at the speed of 0.14-0.2 ℃/min, then cooling to 30-32 ℃ at the speed of 0.08-0.1 ℃/min, keeping the temperature for 2.5-4h, and discharging mother liquor; crystal sweating, wherein the sweating temperature rise rate is 0.05-0.06 ℃/min, the sweating final temperature is 45 ℃, and sweat is discharged; heating to melt the crystals and collecting the product;
the process flow for obtaining the 3,3 ', 4, 4' -tetramethyl biphenyl with the purity of more than 99.5 percent through a melt crystallization procedure is as follows: heating the material to 75 ℃ for melting, adding the material into a box-type melting crystallizer, cooling to 64-68 ℃ at the speed of 0.12-0.2 ℃/min, then cooling to 58-60 ℃ at the speed of 0.08-0.1 ℃/min, keeping the temperature for 1.5-2h, and discharging mother liquor; crystal sweating, wherein the sweating temperature rise rate is 0.07-0.08 ℃/min, the sweating final temperature is 75 ℃, and sweat is discharged; and heating to melt the crystals and collect the product.
2. The method for separating the high-purity isomer of tetramethyl biphenyl by rectification-melt crystallization coupling according to claim 1, wherein the mother liquor and sweat are subjected to a melt crystallization procedure.
3. The method for separating the high-purity isomer of tetramethylbiphenyl by rectification-melt crystallization coupled separation according to claim 1, wherein the qualified product with the purity of more than 99.5% obtained in step (2) is subjected to re-melt crystallization to obtain a high-quality product with the purity of 99.9999%.
4. The method for separating the high-purity isomer of tetramethylbiphenyl by rectification-melt crystallization coupling according to claim 3, wherein the remelting crystallization is performed by a falling film crystallizer or a suspension crystallizer.
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Denomination of invention: Method for Separation of High Purity Isomers of Tetramethylbiphenyl by Distillation Melt Crystallization Coupling Effective date of registration: 20231109 Granted publication date: 20211026 Pledgee: Dongying Hekou District sub branch of China Post Savings Bank Co.,Ltd. Pledgor: SHANDONG GUANSEN POLYMERS MATERIALS SCIENCE AND TECHNOLOGY Inc. Registration number: Y2023980065013 |