CN109776321B - Purification method and decolorization method of 1, 4-cyclohexane dimethyl phthalate crude product - Google Patents
Purification method and decolorization method of 1, 4-cyclohexane dimethyl phthalate crude product Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 69
- 239000012043 crude product Substances 0.000 title claims abstract description 31
- 238000000746 purification Methods 0.000 title claims abstract description 23
- NIQCNGHVCWTJSM-UHFFFAOYSA-N Dimethyl phthalate Chemical compound COC(=O)C1=CC=CC=C1C(=O)OC NIQCNGHVCWTJSM-UHFFFAOYSA-N 0.000 title abstract description 72
- FBSAITBEAPNWJG-UHFFFAOYSA-N dimethyl phthalate Natural products CC(=O)OC1=CC=CC=C1OC(C)=O FBSAITBEAPNWJG-UHFFFAOYSA-N 0.000 title abstract description 36
- 229960001826 dimethylphthalate Drugs 0.000 title abstract description 36
- 238000004042 decolorization Methods 0.000 title description 6
- 239000012535 impurity Substances 0.000 claims abstract description 90
- 238000009835 boiling Methods 0.000 claims abstract description 58
- PXGZQGDTEZPERC-UHFFFAOYSA-N 1,4-cyclohexanedicarboxylic acid Chemical compound OC(=O)C1CCC(C(O)=O)CC1 PXGZQGDTEZPERC-UHFFFAOYSA-N 0.000 claims abstract description 57
- 239000000047 product Substances 0.000 claims abstract description 54
- LNGAGQAGYITKCW-UHFFFAOYSA-N dimethyl cyclohexane-1,4-dicarboxylate Chemical compound COC(=O)C1CCC(C(=O)OC)CC1 LNGAGQAGYITKCW-UHFFFAOYSA-N 0.000 claims description 69
- 238000010992 reflux Methods 0.000 claims description 30
- 239000000498 cooling water Substances 0.000 claims description 28
- WOZVHXUHUFLZGK-UHFFFAOYSA-N dimethyl terephthalate Chemical compound COC(=O)C1=CC=C(C(=O)OC)C=C1 WOZVHXUHUFLZGK-UHFFFAOYSA-N 0.000 claims description 26
- 239000002253 acid Substances 0.000 claims description 21
- 150000007513 acids Chemical class 0.000 claims description 21
- XEKOWRVHYACXOJ-UHFFFAOYSA-N Ethyl acetate Chemical compound CCOC(C)=O XEKOWRVHYACXOJ-UHFFFAOYSA-N 0.000 claims description 18
- KKEYFWRCBNTPAC-UHFFFAOYSA-N Terephthalic acid Chemical compound OC(=O)C1=CC=C(C(O)=O)C=C1 KKEYFWRCBNTPAC-UHFFFAOYSA-N 0.000 claims description 14
- 238000003860 storage Methods 0.000 claims description 13
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 claims description 12
- 238000004519 manufacturing process Methods 0.000 claims description 12
- FERIUCNNQQJTOY-UHFFFAOYSA-N Butyric acid Chemical compound CCCC(O)=O FERIUCNNQQJTOY-UHFFFAOYSA-N 0.000 claims description 6
- OFOBLEOULBTSOW-UHFFFAOYSA-N Malonic acid Chemical compound OC(=O)CC(O)=O OFOBLEOULBTSOW-UHFFFAOYSA-N 0.000 claims description 6
- WNLRTRBMVRJNCN-UHFFFAOYSA-N adipic acid Chemical compound OC(=O)CCCCC(O)=O WNLRTRBMVRJNCN-UHFFFAOYSA-N 0.000 claims description 6
- XBDQKXXYIPTUBI-UHFFFAOYSA-N dimethylselenoniopropionate Natural products CCC(O)=O XBDQKXXYIPTUBI-UHFFFAOYSA-N 0.000 claims description 6
- RTBFRGCFXZNCOE-UHFFFAOYSA-N 1-methylsulfonylpiperidin-4-one Chemical compound CS(=O)(=O)N1CCC(=O)CC1 RTBFRGCFXZNCOE-UHFFFAOYSA-N 0.000 claims description 3
- KDYFGRWQOYBRFD-UHFFFAOYSA-N Succinic acid Natural products OC(=O)CCC(O)=O KDYFGRWQOYBRFD-UHFFFAOYSA-N 0.000 claims description 3
- 239000001361 adipic acid Substances 0.000 claims description 3
- 235000011037 adipic acid Nutrition 0.000 claims description 3
- JFCQEDHGNNZCLN-UHFFFAOYSA-N anhydrous glutaric acid Natural products OC(=O)CCCC(O)=O JFCQEDHGNNZCLN-UHFFFAOYSA-N 0.000 claims description 3
- KDYFGRWQOYBRFD-NUQCWPJISA-N butanedioic acid Chemical compound O[14C](=O)CC[14C](O)=O KDYFGRWQOYBRFD-NUQCWPJISA-N 0.000 claims description 3
- 125000005842 heteroatom Chemical group 0.000 claims description 3
- 235000019260 propionic acid Nutrition 0.000 claims description 3
- IUVKMZGDUIUOCP-BTNSXGMBSA-N quinbolone Chemical compound O([C@H]1CC[C@H]2[C@H]3[C@@H]([C@]4(C=CC(=O)C=C4CC3)C)CC[C@@]21C)C1=CCCC1 IUVKMZGDUIUOCP-BTNSXGMBSA-N 0.000 claims description 3
- 238000005292 vacuum distillation Methods 0.000 claims 3
- 239000007788 liquid Substances 0.000 description 15
- 150000002148 esters Chemical class 0.000 description 8
- 230000000694 effects Effects 0.000 description 5
- 239000007791 liquid phase Substances 0.000 description 5
- 239000000203 mixture Substances 0.000 description 5
- 238000007670 refining Methods 0.000 description 5
- 238000013094 purity test Methods 0.000 description 4
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 3
- 238000005265 energy consumption Methods 0.000 description 3
- 229920000728 polyester Polymers 0.000 description 3
- 238000000926 separation method Methods 0.000 description 3
- YIMQCDZDWXUDCA-UHFFFAOYSA-N [4-(hydroxymethyl)cyclohexyl]methanol Chemical compound OCC1CCC(CO)CC1 YIMQCDZDWXUDCA-UHFFFAOYSA-N 0.000 description 2
- 239000006227 byproduct Substances 0.000 description 2
- 238000000576 coating method Methods 0.000 description 2
- 239000002537 cosmetic Substances 0.000 description 2
- 150000005690 diesters Chemical class 0.000 description 2
- 238000004821 distillation Methods 0.000 description 2
- 239000000543 intermediate Substances 0.000 description 2
- 230000016507 interphase Effects 0.000 description 2
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- 239000012071 phase Substances 0.000 description 2
- 229920001225 polyester resin Polymers 0.000 description 2
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- 239000002904 solvent Substances 0.000 description 2
- 239000012808 vapor phase Substances 0.000 description 2
- RYHBNJHYFVUHQT-UHFFFAOYSA-N 1,4-Dioxane Chemical compound C1COCCO1 RYHBNJHYFVUHQT-UHFFFAOYSA-N 0.000 description 1
- 239000004952 Polyamide Substances 0.000 description 1
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 229920000180 alkyd Polymers 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 238000009903 catalytic hydrogenation reaction Methods 0.000 description 1
- 239000013064 chemical raw material Substances 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- GGCUUOGRTPMFQK-UHFFFAOYSA-N dimethyl cyclohexane-1,1-dicarboxylate Chemical compound COC(=O)C1(C(=O)OC)CCCCC1 GGCUUOGRTPMFQK-UHFFFAOYSA-N 0.000 description 1
- 239000000835 fiber Substances 0.000 description 1
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- 239000010687 lubricating oil Substances 0.000 description 1
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- 239000004014 plasticizer Substances 0.000 description 1
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- 239000000126 substance Substances 0.000 description 1
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- 229920006305 unsaturated polyester Polymers 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
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- Heterocyclic Carbon Compounds Containing A Hetero Ring Having Oxygen Or Sulfur (AREA)
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Abstract
The invention provides a purification method and a decoloration method of a 1, 4-cyclohexane dimethyl phthalate crude product. The purification method comprises the step of carrying out vacuum rectification on a 1, 4-cyclohexanedicarboxylate crude product containing impurities by adopting a rectifying tower under a vacuum condition, wherein the vacuum rectification purity comprises a first rectification stage and a second rectification stage, the first rectification stage is used for removing the impurities with the boiling point lower than that of the 1, 4-cyclohexanedicarboxylate, and the second rectification stage is used for removing the impurities with the boiling point higher than that of the 1, 4-cyclohexanedicarboxylate. The purification method realizes effective removal of impurities in the 1, 4-cyclohexane dimethyl phthalate crude product, improves the purity of a target product, and also improves the colored condition of the 1, 4-cyclohexane dimethyl phthalate.
Description
Technical Field
The invention relates to the field of polyester production, and particularly relates to a purification method and a decolorization method of a 1, 4-cyclohexane dimethyl phthalate crude product.
Background
Dimethyl 1, 4-cyclohexanedicarboxylate (DMCD) is an important chemical raw material, is widely used for synthesizing polyester resin, polyamide, alkyd resin, plasticizer and the like, can be independently used as a modifying material of a polymer, and is an intermediate monomer for producing 1, 4-Cyclohexanedimethanol (CHDM). 1, 4-Cyclohexanedimethanol (CHDM) is an important novel polyester production raw material in industry, and is widely used for manufacturing polyester fibers, water-based polyester resins, unsaturated polyesters, polyurethane coatings and foams, lubricating oil, coatings, printing ink, adhesives, medical and cosmetic polymer intermediates, solvents of cosmetics and personal care products, and high-new-property products such as lubricants and hydraulic fluids. Dimethyl 1, 4-cyclohexanedicarboxylate (DMCD) is also of great use in coatings.
Dimethyl 1, 4-cyclohexanedicarboxylate (DMCD) is produced on an industrial scale by direct liquid phase catalytic hydrogenation of dimethyl terephthalate (DMT). The hydrogenation crude product contains unreacted dimethyl terephthalate (DMT) in addition to the target product dimethyl 1, 4-cyclohexanedicarboxylate (DMCD), and also contains a plurality of byproduct light components and a plurality of byproduct heavy components. The boiling point of unreacted dimethyl terephthalate (DMT) raw material, dimethyl 1, 4-cyclohexanedicarboxylate (DMCD) product and other heavy components is higher under normal pressure, and the difficulty of separation and purification is higher when the dimethyl 1, 4-cyclohexanedicarboxylate (DMCD) is refined under the high-temperature condition.
The 1, 4-cyclohexane dimethyl phthalate (CHDM) absorbs or generates a small amount of trace colorless and colored impurities during the use and long-term storage, and has certain influence on the use of the 1, 4-cyclohexane dimethyl phthalate.
The prior art discloses a method for preparing dimethyl cyclohexanedicarboxylate, wherein after a catalyst is removed by filtering reaction mixed liquid, distillation is carried out, and a solvent 1, 4-dioxane is recovered to obtain the dimethyl 1, 4-cyclohexanedicarboxylate. Also discloses a method for condensing and separating the mixture from the reactor to obtain a crude product of the 1, 4-cyclohexane dimethyl dicarboxylate. There is also disclosed a process for the solvent-free preparation of dimethyl 1, 4-cyclohexanedicarboxylate. However, none of these methods provide the process conditions and methods for purifying dimethyl 1, 4-cyclohexanedicarboxylate.
On the basis of the above, the existing method for preparing 1, 4-cyclohexane dimethyl phthalate needs to be improved so as to reduce the content of impurities.
Disclosure of Invention
The invention mainly aims to provide a method for purifying and decoloring a 1, 4-cyclohexane dimethyl phthalate crude product so as to reduce the content of impurities.
In order to achieve the above object, according to one aspect of the present invention, there is provided a method for purifying a crude dimethyl 1, 4-cyclohexanedicarboxylate, the method comprising: the method comprises the following steps of performing reduced pressure rectification on a crude product of the 1, 4-cyclohexanedicarboxylate containing impurities by using a rectification tower under a vacuum condition, wherein the reduced pressure rectification purity comprises a first rectification stage and a second rectification stage, the first rectification stage is used for removing the impurities with the boiling point lower than that of the 1, 4-cyclohexanedicarboxylate, and the second rectification stage is used for removing the impurities with the boiling point higher than that of the 1, 4-cyclohexanedicarboxylate.
Further, under the conditions that the temperature of a tower kettle of the rectifying tower is 150-180 ℃, the temperature of a tower top is 65-165 ℃, the vacuum degree is-0.0920-0.1005 Mpa, the reflux ratio is 20: 1-1: 1, and the temperature of cooling water at the tower top is 20-50 ℃, impurities with the boiling point lower than that of 1, 4-dimethyl cyclohexanedicarboxylate are removed; under the conditions that the temperature of a tower kettle of a rectifying tower is 160-195 ℃, the temperature of a tower top is 120-170 ℃, the vacuum degree is-0.0920-0.1005 Mpa, the reflux ratio is 20: 1-1: 5, and the temperature of cooling water at the tower top is 20-60 ℃, a 1, 4-cyclohexanedicarboxylate product with the content of 1, 4-cyclohexanedicarboxylate of 99.8 percent is obtained, and impurities with the boiling point higher than that of 1, 4-cyclohexanedicarboxylate exist in the kettle residue and are removed.
Further, under the conditions that the temperature of a tower kettle of the rectifying tower is 160-180 ℃, the temperature of a tower top is 120-150 ℃, the vacuum degree is-0.0950-0.1000 Mpa, the reflux ratio is 15: 1-2: 1, and the temperature of cooling water at the tower top is 20-35 ℃, impurities with the boiling point lower than that of 1, 4-dimethyl cyclohexanedicarboxylate are removed.
Further, under the conditions that the temperature of a tower kettle of a rectifying tower is 165-185 ℃, the temperature of a tower top is 120-165 ℃, the vacuum degree is-0.0950-0.1000 Mpa, the reflux ratio is 15: 1-1: 2, and the temperature of cooling water at the tower top is 25-50 ℃, a 1, 4-cyclohexane dicarboxylic acid dimethyl ester product with the content of 1, 4-cyclohexane dicarboxylic acid dimethyl ester being more than 99.8% is obtained, and impurities with the boiling point higher than that of 1, 4-cyclohexane dicarboxylic acid dimethyl ester exist in the kettle residue and are removed.
Further, the impurity-containing crude 1, 4-cyclohexanedicarboxylate is the crude 1, 4-cyclohexanedicarboxylate in the production, use or storage process of the 1, 4-cyclohexanedicarboxylate; or the impurity-containing 1, 4-cyclohexanedicarboxylate crude product is an unqualified product with the purity of less than 99.0 percent after the 1, 4-cyclohexanedicarboxylate product is placed and stored in the production, use or storage process of the 1, 4-cyclohexanedicarboxylate.
Further, impurities with the boiling point lower than that of the 1, 4-cyclohexane dimethyl phthalate are first acids and/or first hetero esters, and the first acids are monobasic acids and/or dibasic acids; preferably, the monoacid is any one or more of acetic acid, propionic acid and butyric acid, the diacid is any one or more of malonic acid, succinic acid, glutaric acid, adipic acid and terephthalic acid, and the first hetereester is ethyl acetate and/or dimethyl terephthalate.
Further, the impurities having boiling points higher than that of dimethyl 1, 4-cyclohexanedicarboxylate are the second acids and/or the second hetero esters.
Further, the vacuum rectification is batch vacuum rectification or continuous vacuum rectification.
In order to achieve the above objects, according to one aspect of the present invention, there is provided a method for decoloring a crude dimethyl 1, 4-cyclohexanedicarboxylate, the method for decoloring using any one of the above purification methods.
By applying the technical scheme of the invention, the 1, 4-cyclohexanedicarboxylate crude product is refined and purified in the rectifying tower, firstly, impurities with the boiling point lower than that of the 1, 4-cyclohexanedicarboxylate in the crude product are rectified out through the first rectifying stage, then, the target product 1, 4-cyclohexanedicarboxylate is rectified and recovered through the second rectifying stage, and the impurities with the boiling point higher than that of the 1, 4-cyclohexanedicarboxylate are remained in the bottom residue of the tower, so that the impurities in the 1, 4-cyclohexanedicarboxylate crude product are effectively removed, the purity of the target product is improved, and the color condition of the 1, 4-cyclohexanedicarboxylate is also improved.
Detailed Description
It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present invention will be described in detail with reference to examples.
The vacuum in this application means gauge pressure.
As mentioned in the background art, the dimethyl 1, 4-cyclohexanedicarboxylate in the prior art contains impurities during the production, use or storage process, and the unqualified dimethyl 1, 4-cyclohexanedicarboxylate after being stored has color due to more impurities, so that the inventors of the present application have intensively studied the existing preparation method and purification method of dimethyl 1, 4-cyclohexanedicarboxylate in order to further improve the purity, reduce the impurities and solve the decolorization problem of the colored dimethyl 1, 4-cyclohexanedicarboxylate, and put forward the technical scheme of the present application.
In one exemplary embodiment of the present application, there is provided a method for purifying dimethyl 1, 4-cyclohexanedicarboxylate, the method comprising: the method comprises the following steps of performing reduced pressure rectification on a crude product of the 1, 4-cyclohexanedicarboxylate containing impurities by using a rectification tower under a vacuum condition, wherein the reduced pressure rectification purity comprises a first rectification stage and a second rectification stage, the first rectification stage is used for removing the impurities with the boiling point lower than that of the 1, 4-cyclohexanedicarboxylate, and the second rectification stage is used for removing the impurities with the boiling point higher than that of the 1, 4-cyclohexanedicarboxylate.
The above purification method of the application, the crude 1, 4-cyclohexanedicarboxylate is refined and purified in the rectifying tower, firstly the impurities with the boiling point lower than that of 1, 4-cyclohexanedicarboxylate (normal pressure is 259 ℃, the boiling point is 132 ℃ at 10 mmHg) in the crude product are rectified out through the first rectifying stage, then the target product 1, 4-cyclohexanedicarboxylate is rectified and recovered through the second rectifying stage, and the impurities with the boiling point higher than that of 1, 4-cyclohexanedicarboxylate are left in the bottom residue of the tower, thereby realizing the effective removal of the impurities in the crude 1, 4-cyclohexanedicarboxylate, improving the purity of the target product, and improving the colored condition of the 1, 4-cyclohexanedicarboxylate.
In the purification method, the specific operating conditions of the first rectification stage and the second rectification stage are reasonably set according to different purposes of the two rectification stages. In a preferred embodiment of the application, the temperature of a tower bottom of the first rectification stage is 150-180 ℃, the temperature of a tower top is 65-165 ℃, the vacuum degree is-0.0920-0.1005 MPa, the reflux ratio is 20: 1-1: 1, and impurities with the boiling point lower than that of 1, 4-dimethyl cyclohexanedicarboxylate are removed under the condition that the temperature of cooling water at the tower top is 20-50 ℃; under the conditions that the temperature of a tower kettle is 160-195 ℃, the temperature of a tower top is 120-170 ℃, the vacuum degree is-0.0920-0.1005 Mpa, the reflux ratio is 20: 1-1: 5, and the temperature of cooling water at the tower top is 20-60 ℃, a 1, 4-cyclohexane dimethyl phthalate product with the content of 1, 4-cyclohexane dimethyl phthalate being more than 99.8 percent is obtained, and impurities with the boiling point higher than that of the 1, 4-cyclohexane dimethyl phthalate exist in kettle residues and are removed.
In the rectification process, gas and liquid in the rectification tower are in contact with each other to carry out interphase mass transfer, a condenser positioned at the top of the tower enables steam to be partially condensed, part of condensed liquid is returned to the tower as reflux liquid, and the rest of distillate is a product at the top of the tower. A reboiler located at the bottom of the column partially vaporizes the liquid, with the vapor rising up the column and the remaining liquid being the overhead product. The feed is loaded into the middle of the column, the liquid in the feed descends the column with the liquid from the upper column section, and the vapor in the feed ascends the column with the vapor from the lower column section. In the whole rectification process, gas-liquid two phases are in countercurrent contact to carry out interphase mass transfer. The more volatile components in the liquid phase enter the vapor phase and the less volatile components in the vapor phase pass into the liquid phase. Rectification by the reflux process enables a more complete separation of the liquid mixture, in that it is carried out. The reflux comprises both the high-concentration volatile component liquid at the top of the column and the high-concentration non-volatile component vapor at the bottom of the column. The gas-liquid reflux forms a gas-liquid two-phase countercurrent contact. The ratio of the amount of liquid refluxed into the column at the top of the column to the amount of product at the top of the column is called the reflux ratio. The reflux ratio influences the effect and energy consumption of rectification separation to a certain extent.
Specifically, in the rectification process of the first rectification stage, the temperature of the bottom of the column, the temperature of the top of the column and the vacuum degree are controlled within the above ranges, so that impurities with the boiling point lower than that of the 1, 4-cyclohexane dimethyl phthalate in the crude product can be removed. The reflux ratio of the first rectification stage is within the range, so that the product separated from the top of the tower can be purer, and further can be more thoroughly separated from the crude product, and the content of the impurity component in the target product is lower. And the cooling water at the top of the tower is condensed by adopting the cooling water with the temperature of 20-50 ℃, so that the method is convenient and has low cost.
According to the purification method, after the first rectification stage is carried out, impurity components with boiling points lower than that of a target product are basically removed, and components with boiling points higher than that of the target product are rectified and separated out through the second rectification stage. In the second distillation stage, the temperature of the bottom of the column, the temperature of the top of the column and the vacuum degree are controlled within the ranges, so that impurities with boiling points higher than that of the 1, 4-cyclohexane dimethyl phthalate in the crude product can be removed. The reflux ratio of the second rectification stage is in the range, so that the steam component which is difficult to volatilize at the bottom of the tower can be more fully transferred into the liquid phase and returned to the tower, and the target product is separated from the top of the tower due to the boiling point of the target product being lower than that of the impurity components, so that the content of the impurity components in the target product is lower. And the cooling water at the top of the tower is condensed by adopting the cooling water with the temperature of 20-60 ℃, so that the method is convenient and has low cost.
In order to further improve the impurity removal effect of the first rectification stage, the inventors further optimize the rectification operation conditions. In a preferred embodiment of the present application, the temperature of the tower bottom of the first rectification stage is 160-180 ℃, the temperature of the tower top is 120-150 ℃, the vacuum degree is-0.0950-0.1000 MPa, the reflux ratio is 15: 1-2: 1, and the temperature of the cooling water at the tower top is 20-35 ℃. The temperature of the tower bottom of the first rectification stage is controlled within the range, so that the low-boiling-point impurity components are more favorably volatilized and separated from the tower top. The reflux ratio of the first rectification stage is within the range, so that the product separated from the top of the tower can be purer, and further can be more thoroughly separated from the crude product, and the content of the impurity component in the target product is lower. And the cooling water at the top of the tower is condensed by adopting the cooling water with the temperature of 20-35 ℃, so that the method is convenient, low in cost and low in energy consumption.
In order to further improve the impurity removal effect of the second rectification stage, the inventors further optimize the rectification operation conditions. In a preferred embodiment of the present application, the temperature of the bottom of the second rectification stage is 165-185 ℃, the temperature of the top of the second rectification stage is 120-165 ℃, the vacuum degree is-0.0950-0.1000 MPa, the reflux ratio is 15: 1-1: 2, and the temperature of the cooling water at the top of the second rectification stage is 25-50 ℃. By controlling the temperature of the tower bottom, the temperature of the tower top and the vacuum degree within the above ranges, impurities with boiling points higher than that of the 1, 4-dimethyl cyclohexanedicarboxylate in the crude product can be removed relatively more thoroughly. The reflux ratio of the second rectification stage is in the range, so that the steam component which is difficult to volatilize at the bottom of the tower can be more fully transferred into the liquid phase and returned to the tower, and the target product is separated from the top of the tower due to the boiling point of the target product being lower than that of the impurity components, so that the content of the impurity components in the target product is lower. The cooling water at the top of the tower is condensed by the cooling water at the temperature of 25-50 ℃, so that the operation is convenient and the energy consumption is low.
In the crude product of the 1, 4-cyclohexanedicarboxylic acid dimethyl ester containing impurities, the impurity components have certain differences according to different production methods, storage modes and storage time. The impurity-containing 1, 4-cyclohexanedicarboxylate crude product is a 1, 4-cyclohexanedicarboxylate crude product in the production, use or storage process of 1, 4-cyclohexanedicarboxylate; or the impurity-containing 1, 4-cyclohexanedicarboxylate crude product is an unqualified product with the purity of less than 99.0 percent after the 1, 4-cyclohexanedicarboxylate product is placed and stored in the production, use or storage process of the 1, 4-cyclohexanedicarboxylate.
In a preferred embodiment herein, the impurities having a boiling point lower than that of dimethyl 1, 4-cyclohexanedicarboxylate are first acids and/or first heteroesters, the first acids being monobasic and/or dibasic acids; preferably, the monoacid is any one or more of acetic acid, propionic acid and butyric acid, the diacid is any one or more of malonic acid, succinic acid, glutaric acid, adipic acid and terephthalic acid, and the first hetereester is ethyl acetate and/or dimethyl terephthalate.
By utilizing the refining and purifying method, the impurities with the boiling point lower than that of the 1, 4-cyclohexane dimethyl phthalate can be effectively removed, so that the obtained colorless or nearly colorless qualified product with the content of the 1, 4-cyclohexane dimethyl phthalate greater than 99.8 percent is obtained.
In a preferred embodiment herein, the impurities having a boiling point higher than that of dimethyl 1, 4-cyclohexanedicarboxylate are second acids and/or second heteroesters. By utilizing the refining and purifying method, the impurities with the boiling point higher than that of the 1, 4-cyclohexane dimethyl phthalate can be effectively removed, so that the obtained colorless or nearly colorless qualified product with the content of the 1, 4-cyclohexane dimethyl phthalate greater than 99.8 percent is obtained.
The second fusel alcohol and the second diester are relatively complex in composition, and specific structures or compositions can be obtained through chemical analysis, which is not listed here. It was determined that the second fusel alcohol and the second diester impurity share the common characteristic of having boiling points higher than that of dimethyl 1, 4-cyclohexanedicarboxylate, which is significantly different from the first fusel alcohol and the first fusel ester in terms of composition and boiling point properties.
In the refining and purifying method, the vacuum rectification can be intermittent vacuum rectification or continuous vacuum rectification. No matter what rectification method is adopted, the target product can be effectively purified, so that the content of the 1, 4-cyclohexane dimethyl dicarboxylate in the target product is more than 99.8 percent, and the target product is colorless or nearly colorless in a molten state.
In another exemplary embodiment of the present application, there is also provided a method for decoloring a crude 1, 4-cyclohexanedicarboxylic acid dimethyl ester, wherein the decoloring is performed by any one of the above-mentioned purification methods. The decolorization method enables the content of 1, 4-cyclohexane dimethyl dicarboxylate in the target product to be more than 99.8 percent, and the target product is colorless or nearly colorless in a molten state.
The advantageous effects of the present application will be further described with reference to specific examples.
Examples 1 to 7
Dimethyl 1, 4-cyclohexanedicarboxylate containing acids, miscellaneous esters and other impurities, wherein the content of terephthalic acid is 0.20%, the content of ethyl acetate is 0.29%, the content of dimethyl terephthalate is 0.12%, the purity of dimethyl 1, 4-cyclohexanedicarboxylate is 97.27%, and the balance is colorless or colored impurities with the boiling point lower than or higher than that of dimethyl 1, 4-cyclohexanedicarboxylate.
Intermittently or continuously rectifying the impurity-containing 1, 4-dimethyl cyclohexanedicarboxylate by a rectifying tower under reduced pressure, and removing impurities with the boiling point lower than that of the 1, 4-dimethyl cyclohexanedicarboxylate under the conditions that the temperature of a tower kettle is 150-180 ℃, the temperature of a tower top is 65-165 ℃, the vacuum degree is-0.0920-0.1005 Mpa, the reflux ratio is 20: 1-1: 1 and the temperature of cooling water at the tower top is 20-50 ℃.
Under the conditions that the temperature of a tower kettle is 160-195 ℃, the temperature of a tower top is 120-170 ℃, the vacuum degree is-0.0920-0.1005 Mpa, the reflux ratio is 20: 1-1: 5, and the temperature of cooling water at the tower top is 20-60 ℃, a qualified 1, 4-cyclohexane dimethyl phthalate product with the content of 1, 4-cyclohexane dimethyl phthalate of more than 99.8 percent is obtained, and impurities with the boiling point higher than that of 1, 4-cyclohexane dimethyl phthalate exist in kettle residues and are removed.
Table 1: purity test of rectified dimethyl 1, 4-cyclohexanedicarboxylate product
Examples 8 to 13
Dimethyl 1, 4-cyclohexanedicarboxylate containing acids, miscellaneous esters and other impurities, wherein the content of terephthalic acid is 0.26%, the content of ethyl acetate is 3.04%, the content of dimethyl terephthalate is 1.03%, the purity of dimethyl 1, 4-cyclohexanedicarboxylate is 90.53%, and the balance is colorless or colored impurities with the boiling point lower than or higher than that of dimethyl 1, 4-cyclohexanedicarboxylate.
Intermittently or continuously rectifying the impurity-containing 1, 4-dimethyl cyclohexanedicarboxylate by a rectifying tower under reduced pressure, and removing impurities with the boiling point lower than that of the 1, 4-dimethyl cyclohexanedicarboxylate under the conditions that the temperature of a tower kettle is 150-180 ℃, the temperature of a tower top is 65-165 ℃, the vacuum degree is-0.0920-0.1005 Mpa, the reflux ratio is 20: 1-1: 1 and the temperature of cooling water at the tower top is 20-50 ℃.
Under the conditions that the temperature of a tower kettle is 160-195 ℃, the temperature of a tower top is 120-170 ℃, the vacuum degree is-0.0920-0.1000 Mpa, the reflux ratio is 20: 1-5: 1, and the temperature of cooling water at the tower top is 20-60 ℃, a qualified 1, 4-cyclohexane dimethyl phthalate product with the content of 1, 4-cyclohexane dimethyl phthalate of more than 99.8 percent is obtained, and impurities with the boiling point higher than that of 1, 4-cyclohexane dimethyl phthalate exist in kettle residues and are removed.
Table 2: purity test of rectified dimethyl 1, 4-cyclohexanedicarboxylate product
Examples 14 to 18
The dimethyl 1, 4-cyclohexanedicarboxylate containing acids, miscellaneous esters and other impurities, wherein the content of terephthalic acid is 0.17%, the content of acetic acid is 0.08%, the content of ethyl acetate is 0.05%, the content of dimethyl terephthalate is 1.16%, the purity of dimethyl 1, 4-cyclohexanedicarboxylate is 95.63%, and the rest components are colorless or colored impurities with the boiling point lower than or higher than that of dimethyl 1, 4-cyclohexanedicarboxylate.
Intermittently or continuously rectifying the 1, 4-cyclohexane dimethyl phthalate containing impurities by adopting a rectifying tower under reduced pressure, and removing the impurities with the boiling point lower than that of the 1, 4-cyclohexane dimethyl phthalate under the conditions that the temperature of a tower kettle is 160-180 ℃, the temperature of a tower top is 120-150 ℃, the vacuum degree is-0.0950-0.1000 Mpa, the reflux ratio is 15: 1-2: 1 and the temperature of cooling water at the tower top is 20-35 ℃.
And obtaining a qualified 1, 4-cyclohexane dimethyl phthalate product with the content of 1, 4-cyclohexane dimethyl phthalate being more than 99.8 percent under the conditions that the temperature of a tower kettle is 165-185 ℃, the temperature of a tower top is 120-165 ℃, the vacuum degree is-0.0950-0.1000 Mpa, the reflux ratio is 15: 1-1: 2 and the temperature of cooling water at the tower top is 25-50 ℃, wherein impurities with the boiling point higher than that of 1, 4-cyclohexane dimethyl phthalate exist in kettle residues and are removed.
Table 3: purity test of rectified dimethyl 1, 4-cyclohexanedicarboxylate product
Examples 19 to 25
Dimethyl 1, 4-cyclohexanedicarboxylate containing acids, miscellaneous esters and other impurities, wherein the content of terephthalic acid is 0.22%, the content of dimethyl terephthalate is 0.71%, the purity of dimethyl 1, 4-cyclohexanedicarboxylate is 97.37%, and the rest components are colorless or colored impurities with the boiling point lower than or higher than that of dimethyl 1, 4-cyclohexanedicarboxylate.
Intermittently or continuously rectifying the 1, 4-cyclohexane dimethyl phthalate containing impurities by adopting a rectifying tower under reduced pressure, and removing the impurities with the boiling point lower than that of the 1, 4-cyclohexane dimethyl phthalate under the conditions that the temperature of a tower kettle is 160-180 ℃, the temperature of a tower top is 120-150 ℃, the vacuum degree is-0.0950-0.1000 Mpa, the reflux ratio is 15: 1-2: 1 and the temperature of cooling water at the tower top is 20-35 ℃.
And obtaining a qualified 1, 4-cyclohexane dimethyl phthalate product with the content of 1, 4-cyclohexane dimethyl phthalate being more than 99.8 percent under the conditions that the temperature of a tower kettle is 165-185 ℃, the temperature of a tower top is 120-165 ℃, the vacuum degree is-0.0950-0.1000 Mpa, the reflux ratio is 15: 1-1: 2 and the temperature of cooling water at the tower top is 25-50 ℃, wherein impurities with the boiling point higher than that of 1, 4-cyclohexane dimethyl phthalate exist in kettle residues and are removed.
Table 4: purity test of rectified dimethyl 1, 4-cyclohexanedicarboxylate product
From the above description, it can be seen that the above-described embodiments of the present application achieve the following technical effects: the method adopts a vacuum rectification method to refine and purify the 1, 4-cyclohexanedicarboxylate containing acids, miscellaneous esters and other colorless or colored impurities with the boiling point lower than or higher than that of the 1, 4-cyclohexanedicarboxylate dimethyl ester, and can obtain a colorless or nearly colorless qualified 1, 4-cyclohexanedicarboxylate dimethyl ester product with the content of the 1, 4-cyclohexanedicarboxylate dimethyl ester being more than 99.8 percent.
The method comprises the steps of performing intermittent or continuous vacuum rectification on the 1, 4-cyclohexanedicarboxylate containing impurities by using a rectifying tower, removing acids, miscellaneous esters and other impurities with the boiling point lower than the boiling point of the 1, 4-cyclohexanedicarboxylate, and obtaining a qualified 1, 4-cyclohexanedicarboxylate product, wherein the acids, miscellaneous esters and other impurities with the boiling point higher than the boiling point of the 1, 4-cyclohexanedicarboxylate exist in kettle residues and are removed.
The method can realize the refining and purification of the crude product and the product of the 1, 4-cyclohexanedicarboxylate containing impurities in the production, use or storage process and the unqualified 1, 4-cyclohexanedicarboxylate after storage, can realize the decolorization of the colored 1, 4-cyclohexanedicarboxylate, and the 1, 4-cyclohexanedicarboxylate product obtained after refining and purification is colorless or nearly colorless transparent liquid in a molten state. The 1, 4-dimethyl cyclohexanedicarboxylate purified by the method has good storage resistance, various indexes are qualified and stable, and downstream use of the 1, 4-dimethyl cyclohexanedicarboxylate can be well met.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (9)
1. A method for purifying a crude product of 1, 4-cyclohexanedicarboxylic acid dimethyl ester, which is characterized by comprising the following steps:
the method comprises the following steps of carrying out reduced pressure rectification on a crude product of the 1, 4-cyclohexanedicarboxylate containing impurities by adopting a rectifying tower under a vacuum condition, wherein the reduced pressure rectification purity comprises a first rectification stage and a second rectification stage, the first rectification stage is used for removing the impurities with the boiling point lower than that of the 1, 4-cyclohexanedicarboxylate, and the second rectification stage is used for removing the impurities with the boiling point higher than that of the 1, 4-cyclohexanedicarboxylate.
2. The purification method according to claim 1,
under the conditions that the temperature of a tower kettle of the rectifying tower is 150-180 ℃, the temperature of a tower top is 65-165 ℃, the vacuum degree is-0.0920-0.1005 Mpa, the reflux ratio is 20: 1-1: 1, and the temperature of cooling water at the tower top is 20-50 ℃, impurities with the boiling point lower than that of 1, 4-dimethyl cyclohexanedicarboxylate are removed;
under the conditions that the temperature of a tower kettle of the rectifying tower is 160-195 ℃, the temperature of a tower top is 120-170 ℃, the vacuum degree is-0.0920-0.1005 Mpa, the reflux ratio is 20: 1-1: 5, and the temperature of cooling water at the tower top is 20-60 ℃, a 1, 4-cyclohexanedicarboxylate product with the content of 1, 4-cyclohexanedicarboxylate of 99.8 percent is obtained, and impurities with the boiling point higher than that of 1, 4-cyclohexanedicarboxylate exist in a kettle residue and are removed.
3. The purification method according to claim 2, wherein the impurities having a boiling point lower than that of dimethyl 1, 4-cyclohexanedicarboxylate are removed under the conditions that the temperature of a bottom of the rectification column is 160 to 180 ℃, the temperature of a top of the rectification column is 120 to 150 ℃, the vacuum degree is-0.0950 to-0.1000 MPa, the reflux ratio is 15:1 to 2:1, and the temperature of cooling water at the top of the rectification column is 20 to 35 ℃.
4. The purification method according to claim 2, wherein a dimethyl 1, 4-cyclohexanedicarboxylate product having a dimethyl 1, 4-cyclohexanedicarboxylate content of 99.8% is obtained under conditions of a rectifying tower having a tower still temperature of 165 to 185 ℃, a tower top temperature of 120 to 165 ℃, a vacuum degree of-0.0950 to-0.1000 Mpa, a reflux ratio of 15:1 to 1:2, and a tower top cooling water temperature of 25 to 50 ℃, and the impurities having a boiling point higher than that of dimethyl 1, 4-cyclohexanedicarboxylate are removed from the still residue.
5. The purification method according to any one of claims 1 to 4,
the impurity-containing 1, 4-cyclohexanedicarboxylate crude product is a 1, 4-cyclohexanedicarboxylate crude product in the production, use or storage process of 1, 4-cyclohexanedicarboxylate; or
The impurity-containing 1, 4-cyclohexanedicarboxylate crude product is an unqualified product with the purity of less than 99.0 percent after the 1, 4-cyclohexanedicarboxylate product is placed and stored in the production, use or storage process of 1, 4-cyclohexanedicarboxylate.
6. The purification method according to any one of claims 1 to 3, wherein the impurities having a boiling point lower than that of dimethyl 1, 4-cyclohexanedicarboxylate are first acids and/or first hetero esters, the first acids being monobasic acids and/or dibasic acids;
preferably, the monoacid is any one or more of acetic acid, propionic acid and butyric acid, the diacid is any one or more of malonic acid, succinic acid, glutaric acid, adipic acid and terephthalic acid, and the first hetereesters are ethyl acetate and/or dimethyl terephthalate.
7. Purification process according to claim 1, 2 or 4, characterized in that the impurities having a boiling point higher than that of dimethyl 1, 4-cyclohexanedicarboxylate are second acids and/or second heteroesters.
8. The purification method according to claim 1, wherein the vacuum distillation is a batch vacuum distillation or a continuous vacuum distillation.
9. A method for decoloring a crude 1, 4-cyclohexanedicarboxylic acid dimethyl ester, which is characterized in that the decoloring method is performed by the purification method according to any one of claims 1 to 8.
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