CN114478343B - Refining and purifying method of caprolactam - Google Patents
Refining and purifying method of caprolactam Download PDFInfo
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- CN114478343B CN114478343B CN202210178523.XA CN202210178523A CN114478343B CN 114478343 B CN114478343 B CN 114478343B CN 202210178523 A CN202210178523 A CN 202210178523A CN 114478343 B CN114478343 B CN 114478343B
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- JBKVHLHDHHXQEQ-UHFFFAOYSA-N epsilon-caprolactam Chemical compound O=C1CCCCCN1 JBKVHLHDHHXQEQ-UHFFFAOYSA-N 0.000 title claims abstract description 368
- 238000000034 method Methods 0.000 title claims abstract description 66
- 238000007670 refining Methods 0.000 title claims abstract description 48
- 238000002425 crystallisation Methods 0.000 claims abstract description 51
- 230000008025 crystallization Effects 0.000 claims abstract description 51
- 239000000463 material Substances 0.000 claims abstract description 44
- 239000000047 product Substances 0.000 claims abstract description 41
- 238000001816 cooling Methods 0.000 claims abstract description 32
- 230000035900 sweating Effects 0.000 claims abstract description 25
- 239000002904 solvent Substances 0.000 claims abstract description 16
- 210000004243 sweat Anatomy 0.000 claims abstract description 13
- 239000012043 crude product Substances 0.000 claims abstract description 7
- 239000012071 phase Substances 0.000 claims description 19
- VEZUQRBDRNJBJY-UHFFFAOYSA-N cyclohexanone oxime Chemical compound ON=C1CCCCC1 VEZUQRBDRNJBJY-UHFFFAOYSA-N 0.000 claims description 16
- 230000008707 rearrangement Effects 0.000 claims description 14
- 238000006243 chemical reaction Methods 0.000 claims description 10
- 238000010438 heat treatment Methods 0.000 claims description 10
- 238000004321 preservation Methods 0.000 claims description 7
- 238000000746 purification Methods 0.000 claims description 7
- 239000013078 crystal Substances 0.000 claims description 5
- 239000003054 catalyst Substances 0.000 claims description 4
- 239000012808 vapor phase Substances 0.000 claims description 4
- 239000007789 gas Substances 0.000 description 14
- 238000004821 distillation Methods 0.000 description 12
- 230000000052 comparative effect Effects 0.000 description 11
- 239000012535 impurity Substances 0.000 description 9
- 238000011084 recovery Methods 0.000 description 6
- 239000012286 potassium permanganate Substances 0.000 description 5
- 238000010521 absorption reaction Methods 0.000 description 4
- 239000003513 alkali Substances 0.000 description 4
- JHIVVAPYMSGYDF-UHFFFAOYSA-N cyclohexanone Chemical compound O=C1CCCCC1 JHIVVAPYMSGYDF-UHFFFAOYSA-N 0.000 description 4
- 238000011534 incubation Methods 0.000 description 4
- 239000007788 liquid Substances 0.000 description 4
- 238000002360 preparation method Methods 0.000 description 4
- 238000000926 separation method Methods 0.000 description 4
- 239000002699 waste material Substances 0.000 description 4
- 238000006237 Beckmann rearrangement reaction Methods 0.000 description 3
- 238000009835 boiling Methods 0.000 description 3
- 239000002994 raw material Substances 0.000 description 3
- ZWXPDGCFMMFNRW-UHFFFAOYSA-N N-methylcaprolactam Chemical compound CN1CCCCCC1=O ZWXPDGCFMMFNRW-UHFFFAOYSA-N 0.000 description 2
- 239000012159 carrier gas Substances 0.000 description 2
- 239000002178 crystalline material Substances 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000007791 liquid phase Substances 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 238000006462 rearrangement reaction Methods 0.000 description 2
- 238000001953 recrystallisation Methods 0.000 description 2
- OSKXXXKQSBKDLR-UHFFFAOYSA-N 1,2,3,4,4a,5,5a,6,7,8-decahydrophenazine Chemical compound C1CCC2NC(CCCC3)C3=NC2=C1 OSKXXXKQSBKDLR-UHFFFAOYSA-N 0.000 description 1
- FSHMPNBRNOGDDK-UHFFFAOYSA-N 1,2,3,4,4a,5,5a,6-octahydrophenazine Chemical compound C1=CCC2NC(CCCC3)C3=NC2=C1 FSHMPNBRNOGDDK-UHFFFAOYSA-N 0.000 description 1
- JYJURPHZXCLFDX-UHFFFAOYSA-N 2-methoxycyclohexan-1-one Chemical compound COC1CCCCC1=O JYJURPHZXCLFDX-UHFFFAOYSA-N 0.000 description 1
- VYUKCVLHGXBZDF-UHFFFAOYSA-N 3-methoxycyclohexan-1-one Chemical compound COC1CCCC(=O)C1 VYUKCVLHGXBZDF-UHFFFAOYSA-N 0.000 description 1
- DNXIQMQGKSQHPC-UHFFFAOYSA-N 7-methoxy-3,4,5,6-tetrahydro-2h-azepine Chemical compound COC1=NCCCCC1 DNXIQMQGKSQHPC-UHFFFAOYSA-N 0.000 description 1
- JYYRTWNCBVRKMN-UHFFFAOYSA-N Octahydrophenazine Natural products C1CCCC2=C1N=C1CCCCC1=N2 JYYRTWNCBVRKMN-UHFFFAOYSA-N 0.000 description 1
- 239000004952 Polyamide Substances 0.000 description 1
- -1 adipoyl imine Chemical class 0.000 description 1
- BFNBIHQBYMNNAN-UHFFFAOYSA-N ammonium sulfate Chemical compound N.N.OS(O)(=O)=O BFNBIHQBYMNNAN-UHFFFAOYSA-N 0.000 description 1
- 229910052921 ammonium sulfate Inorganic materials 0.000 description 1
- 235000011130 ammonium sulphate Nutrition 0.000 description 1
- 239000002585 base Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 238000005119 centrifugation Methods 0.000 description 1
- 239000013064 chemical raw material Substances 0.000 description 1
- FWFSEYBSWVRWGL-UHFFFAOYSA-N cyclohex-2-enone Chemical compound O=C1CCCC=C1 FWFSEYBSWVRWGL-UHFFFAOYSA-N 0.000 description 1
- 230000018044 dehydration Effects 0.000 description 1
- 238000006297 dehydration reaction Methods 0.000 description 1
- 238000006356 dehydrogenation reaction Methods 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 229920006351 engineering plastic Polymers 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 238000004817 gas chromatography Methods 0.000 description 1
- 230000007062 hydrolysis Effects 0.000 description 1
- 238000006460 hydrolysis reaction Methods 0.000 description 1
- LCXYEPLVWLASCI-UHFFFAOYSA-N n-methoxycyclohexanimine Chemical compound CON=C1CCCCC1 LCXYEPLVWLASCI-UHFFFAOYSA-N 0.000 description 1
- 229920001778 nylon Polymers 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 229920002647 polyamide Polymers 0.000 description 1
- 239000007858 starting material Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- HIFJUMGIHIZEPX-UHFFFAOYSA-N sulfuric acid;sulfur trioxide Chemical compound O=S(=O)=O.OS(O)(=O)=O HIFJUMGIHIZEPX-UHFFFAOYSA-N 0.000 description 1
Classifications
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07D—HETEROCYCLIC COMPOUNDS
- C07D201/00—Preparation, separation, purification or stabilisation of unsubstituted lactams
- C07D201/16—Separation or purification
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07D—HETEROCYCLIC COMPOUNDS
- C07D223/00—Heterocyclic compounds containing seven-membered rings having one nitrogen atom as the only ring hetero atom
- C07D223/02—Heterocyclic compounds containing seven-membered rings having one nitrogen atom as the only ring hetero atom not condensed with other rings
- C07D223/06—Heterocyclic compounds containing seven-membered rings having one nitrogen atom as the only ring hetero atom not condensed with other rings with hetero atoms or with carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, e.g. ester or nitrile radicals, directly attached to ring carbon atoms
- C07D223/08—Oxygen atoms
- C07D223/10—Oxygen atoms attached in position 2
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Other In-Based Heterocyclic Compounds (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
The invention provides a refining and purifying method of caprolactam. The refining and purifying method comprises the following steps: step S1, carrying out negative pressure rectification on a caprolactam crude product, collecting a first fraction at a first rectification temperature, collecting a second fraction at a second rectification temperature, and collecting a caprolactam fraction at a third rectification temperature, wherein the first rectification temperature is 50-70 ℃, the second rectification temperature is 71-95 ℃, and the third rectification temperature is 96-110 ℃; s2, cooling and crystallizing the caprolactam fraction to obtain a caprolactam crystallization material; step S3, sweating the caprolactam crystallization material, removing sweat, and collecting the rest material to obtain a caprolactam product. By adopting the technical scheme of the invention, the caprolactam crude product is purified by negative pressure rectification, cooling crystallization and sweating in sequence to obtain a high-purity caprolactam product, and the whole process does not adopt a solvent, so that the method is more environment-friendly and safer, and the refining cost of caprolactam is effectively saved.
Description
Technical Field
The invention relates to the technical field of petrochemical industry, in particular to a refining and purifying method of caprolactam.
Background
Caprolactam is an important organic chemical raw material and is mainly used for producing polyamide slices of nylon fibers and engineering plastics. The current caprolactam production method mainly utilizes a liquid phase method of fuming sulfuric acid and a gas phase Beckmann rearrangement process catalyzed by an MFI structure catalyst, and the gas phase rearrangement reaction is environment-friendly and is more and more concerned because low-value ammonium sulfate is not byproduct.
Caprolactam produced by the gas phase rearrangement process contains a wide variety of impurities, which are mainly derived from three aspects, the first solvent production: impurities resulting from the reaction of the solvent with the starting material, product, etc., such as: o-methyl cyclohexanone oxime, N-methyl caprolactam, O-methyl caprolactam, and the like; the raw materials of the second aspect are produced: unreacted raw materials, impurities generated by hydrolysis and dehydration of raw materials, and the like, such as: cyclohexanone oxime, cyclohexanone, octahydrophenazine, decahydrophenazine, and the like; the third aspect product yields: impurities produced by reactions such as dehydrogenation and oxidation of caprolactam, such as: 1-aza-1-cyclohepten-2-one, adipoyl imine, and the like. These impurities affect the product quality of caprolactam and therefore require refining purification of caprolactam. Some researchers dissolve the gas-phase rearrangement product to be refined in a crystallization solvent, and then obtain refined caprolactam through crystallization, solid-liquid separation, desolventizing and distillation.
Disclosure of Invention
The invention mainly aims to provide a refining and purifying method of caprolactam, which aims to solve the technical problems that the existing method for dissolving a gas phase rearrangement product by using a crystallization solvent easily causes pollution of the solvent to the product and three wastes are discharged in the recovery process of the recrystallization solvent, so that the refining cost of the caprolactam is increased.
In order to achieve the above object, according to an aspect of the present invention, there is provided a refining and purifying method of caprolactam, comprising:
Step S1, carrying out negative pressure rectification on a caprolactam crude product, collecting a first fraction at a first rectification temperature, collecting a second fraction at a second rectification temperature, and collecting a caprolactam fraction at a third rectification temperature, wherein the first rectification temperature is 50-70 ℃, the second rectification temperature is 71-95 ℃, and the third rectification temperature is 96-110 ℃;
s2, cooling and crystallizing the caprolactam fraction to obtain a caprolactam crystallization material;
step S3, sweating the caprolactam crystallization material, removing sweat, and collecting the rest material to obtain a caprolactam product.
Further, in the above step S1, the pressure of the negative pressure rectification is 0.1 to 1kPa, preferably 0.4 to 0.6kPa.
Further, in the step S2, the temperature of cooling crystallization is 30-60 ℃, and the heat preservation time is 1-10h.
Further, in the step S2, the caprolactam fraction is reduced to the crystallization temperature by adopting a gradient cooling mode, and the gradient cooling rate is 0.15-1 ℃/h.
Further, in the step S3, the caprolactam crystallization material is heated to the sweating temperature in a gradient heating mode, and the gradient heating rate is 0.15-1 ℃/h.
Further, the step S3 includes: subjecting the caprolactam crystalline material to perspiration, collecting a third fraction at a first perspiration temperature, collecting a fourth fraction at a second perspiration temperature, the first perspiration temperature being between 60 and 65 ℃ and the second perspiration temperature being between 66 and 68.9 ℃.
Further, the refining and purifying method further comprises the following steps: the second fraction and/or the third fraction is returned to the step S1 for negative pressure rectification.
Further, the refining and purifying method further comprises the following steps: the fourth fraction returns to the step S2 to be cooled and crystallized.
Further, the crude caprolactam product is obtained by removing the solvent from a reaction solution prepared by vapor phase rearrangement of cyclohexanone oxime.
Further, the above gas phase rearrangement is carried out in a tube reactor, and the reaction temperature of the gas phase rearrangement is 330-400 ℃.
Further, in the tubular reactor, the catalyst is filled in the tubular, the inner diameter of the tubular is 10-28mm, and the length-diameter ratio is 50-500.
By adopting the technical scheme of the invention, the first fraction and the second fraction are removed by controlling different distillation temperatures in the negative pressure rectification process, the caprolactam fraction is cooled and crystallized to obtain a caprolactam crystallization material, and finally the caprolactam crystallization material is subjected to perspiration to remove sweat and collect the residual material to obtain a high-purity caprolactam product, and meanwhile, the solvent is not adopted in the whole process, so that the method is more environment-friendly and safer, and the refining cost of caprolactam is effectively saved.
Detailed Description
It should be noted that, without conflict, the embodiments of the present application and features of the embodiments may be combined with each other. The present application will be described in detail with reference to examples.
As analyzed by the background technology of the application, the existing caprolactam refining method adopts a crystallization solvent to dissolve a gas-phase rearrangement product, and has the technical problems of easily causing pollution of the solvent to the product and three wastes discharge in the recovery process of the recrystallization solvent, thereby increasing the refining cost of the caprolactam. In order to solve the problem, the application provides a refining and purifying method of caprolactam.
In an exemplary embodiment of the present application, the method for refining and purifying caprolactam comprises:
Step S1, carrying out negative pressure rectification on a caprolactam crude product, collecting a first fraction at a first rectification temperature, collecting a second fraction at a second rectification temperature, and collecting a caprolactam fraction at a third rectification temperature, wherein the first rectification temperature is 50-70 ℃, the second rectification temperature is 71-95 ℃, and the third rectification temperature is 96-110 ℃;
s2, cooling and crystallizing the caprolactam fraction to obtain a caprolactam crystallization material;
step S3, sweating the caprolactam crystallization material, and collecting the rest material to obtain a caprolactam product.
According to the caprolactam refining and purifying method provided by the application, the first fraction and the second fraction are removed by controlling different distillation temperatures in the negative pressure rectification process, the caprolactam fraction is cooled and crystallized to obtain a caprolactam crystallization material, the caprolactam crystallization material is subjected to perspiration to remove sweat, and the rest material is collected to obtain a high-purity caprolactam product, and meanwhile, a solvent is not adopted in the whole process, so that the method is more environment-friendly and safer, and the refining cost of caprolactam is effectively saved.
In the step S1, in the negative pressure rectification process, different first rectification temperature, second rectification temperature and third rectification temperature are respectively set from low to high, so as to facilitate removal of low boiling point impurities and high boiling point impurities contained in the caprolactam crude product, obtain caprolactam fraction with higher purity, and facilitate subsequent crystallization and sweating through cooling, thereby obtaining a caprolactam product with high purity.
The above-mentioned first distillation temperature is set to 50-70 deg.c to facilitate the removal of a first fraction comprising at least one of cyclohexanone, cyclohexenone, 2-methoxycyclohexanone and 3-methoxycyclohexanone at a corresponding negative pressure, the second distillation temperature is set to 71-95 deg.c to facilitate the removal of a second fraction comprising at least one of cyclohexanone oxime and N-methylcaprolactam at a corresponding negative pressure, and then the third distillation temperature is set to 96-110 deg.c to collect a caprolactam fraction, and other substances having a higher boiling point are separated from the caprolactam fraction to obtain a caprolactam fraction having a higher caprolactam content.
In addition, by collecting the first fraction and the second fraction separately, the two fractions are also beneficial to respectively carrying out subsequent treatment according to different content of caprolactam contained in the two fractions, and the first fraction is collected at a lower temperature, so that the first fraction contains low content of caprolactam, the first fraction is subsequently subjected to separate recovery treatment, the collection temperature of the second fraction is similar to that of the caprolactam fraction, and part of caprolactam is contained in the second fraction, so that the second fraction is applied to the next recovery treatment to improve the yield of caprolactam products.
And subsequently cooling and crystallizing the caprolactam fraction, removing impurities which are not crystallized through solid-liquid separation to obtain caprolactam crystallization materials, sweating the caprolactam crystallization materials, removing sweat generated through solid-liquid separation, and collecting the rest materials to obtain a high-purity caprolactam product.
Such means of solid-liquid separation include, but are not limited to, filtration and centrifugation.
Typically, but not by way of limitation, the first rectification temperature is, for example, 50 ℃, 52 ℃,55 ℃, 58 ℃, 60 ℃, 62 ℃, 65 ℃, 68 ℃, or 70 ℃; the second rectification temperature is, for example, 71 ℃, 72 ℃, 75 ℃, 78 ℃, 80 ℃, 82 ℃, 85 ℃, 88 ℃, 90 ℃, 92 ℃ or 95 ℃; the third rectification temperature is, for example, 96 ℃, 98 ℃, 100 ℃, 102 ℃, 105 ℃, 108 ℃ or 110 ℃.
In step S1, in order to be able to collect the first fraction, the second fraction and the caprolactam fraction separately by distillation at a lower temperature, it is preferable to control the pressure of the negative pressure distillation to 0.1 to 1kPa, and particularly when the pressure of the negative pressure distillation is controlled to 0.4 to 0.6kPa, it is more advantageous to obtain a caprolactam fraction having a higher caprolactam content.
In the step S2, the lower the crystallization temperature is, the longer the heat preservation time is, the higher the yield of the obtained caprolactam crystallization material is, but the lower the preparation efficiency of the caprolactam crystallization material is, in order to improve the preparation efficiency on the basis of ensuring the higher yield of the caprolactam crystallization material, the temperature of cooling crystallization is preferably set to be 30-60 ℃, the heat preservation time is 1-10h, the crystallization temperature is lower than 30 ℃, the impurity content in the obtained caprolactam crystallization material is high, the purity of the prepared caprolactam product is low, the crystallization temperature is higher than 60 ℃, and the crystallization of the caprolactam fraction is incomplete, so that the yield of the caprolactam product is low. The heat preservation time is shorter than 1h, the crystallization of caprolactam fraction is incomplete, the yield of caprolactam products is low, the heat preservation time is longer than 10h, the yield of caprolactam crystallization materials is obviously improved, and a great amount of manpower and material resources are wasted.
In order to make the crystallization of the caprolactam fraction more complete, in the step S2, the caprolactam fraction is preferably reduced to the crystallization temperature by means of gradient cooling, and especially when the rate of gradient cooling is controlled to be 0.15-1 ℃/h, the yield of the caprolactam crystalline material is higher. When the gradient cooling rate is lower than 0.15 ℃/h, although the crystallization of the caprolactam fraction can be more sufficient, the crystallization efficiency is too low, the yield of the caprolactam product is not obviously improved, and a large amount of manpower and material resources are wasted. When the gradient cooling rate is higher than 1 ℃/h, the crystallization of the caprolactam fraction is insufficient, resulting in a decrease in the yield of caprolactam product.
Typically, but not limited to, in step S1, the pressure of the negative pressure rectification is, for example, 0.1kPa, 0.2kPa, 0.3kPa, 0.4kPa, 0.5kPa, 0.6kPa, 0.7kPa, 0.8kPa, 0.9kPa or 1.0kPa; in step S2, the temperature of cooling crystallization is 30 ℃, 32 ℃, 35 ℃, 38 ℃, 40 ℃, 42 ℃, 45 ℃, 48 ℃, 50 ℃, 52 ℃, 55 ℃, 58 ℃ or 60 ℃ and the heat preservation time is 1h, 2h, 5h, 8h or 10h; the gradient cooling rate is, for example, 0.15 ℃/h, 0.2 ℃/h, 0.3 ℃/h, 0.4 ℃/h, 0.5 ℃/h, 0.8 ℃/h or 1 ℃/h.
In order to make the caprolactam material sweat more completely, in the step S3, the temperature is preferably raised to the sweat temperature by adopting a gradient temperature raising mode, especially when the gradient temperature raising rate is 0.15-1 ℃/h, the caprolactam crystal material sweat more sufficiently, the purity of the prepared caprolactam product is also higher, and when the gradient temperature raising rate is lower than 0.15 ℃/h, although the caprolactam fraction sweat more sufficiently, the sweat efficiency is too low, the yield of the caprolactam product is not obviously improved, and a large amount of manpower and material resources are wasted. When the gradient heating rate is higher than 1 ℃/h, the caprolactam fraction is not sweated sufficiently, resulting in a decrease in purity of the caprolactam product.
In order to more completely remove perspiration from the perspiration of the caprolactam material, it is preferred that step S3 comprises: the caprolactam crystallization material is subjected to perspiration, a third fraction is collected at a first perspiration temperature, a fourth fraction is collected at a second perspiration temperature, wherein the first perspiration temperature is 60-65 ℃, and the second perspiration temperature is 66-68.9 ℃, so that the third fraction and the fourth fraction are further separated from the caprolactam crystallization material, and a caprolactam product with higher purity is obtained.
The third fraction has a caprolactam content of less than 99.5%, the fourth fraction has a caprolactam content of less than 99.9%, and the caprolactam content is higher than that of the third fraction. The different first perspiration temperature and the second perspiration temperature are set to be favorable for separating and collecting fractions with different caprolactam contents, so that the subsequent recovery by adopting different methods is facilitated.
Typically, but not limited to, in step S3, the rate of gradient heating during sweating is, for example, 0.15 ℃/h, 0.2 ℃/h, 0.3 ℃/h, 0.4 ℃/h, 0.5 ℃/h, 0.8 ℃/h or 1.0 ℃/h; the first sweating temperature is 60 ℃, 61 ℃, 62 ℃, 63 ℃, 64 ℃ or 65 ℃, and the second sweating temperature is 66 ℃, 66.5 ℃, 67 ℃, 67.5 ℃, 68 ℃, 68.5 ℃ or 68.9 ℃. In order to further increase the yield of caprolactam product and avoid the loss of caprolactam, the second fraction and/or the third fraction is preferably returned to the step S1 for negative pressure rectification to recover caprolactam mixed in the second fraction and/or the third fraction, and in addition, since the fourth fraction is collected at a higher second sweating temperature, the fourth fraction contains higher caprolactam, the fourth fraction is preferably returned to the step S2 for cooling crystallization to fully recover caprolactam contained in the fourth fraction.
The crude caprolactam product is prepared by removing a solution from a reaction solution prepared by vapor phase rearrangement of cyclohexanone oxime, and the vapor phase rearrangement temperature is 330-400 ℃ to further improve the caprolactam preparation efficiency.
In order to improve the utilization efficiency of energy and reduce the waste of energy, it is preferable that the above-mentioned gas phase rearrangement is performed in a tube reactor to heat the carrier gas containing cyclohexanone oxime by using the heat released during the gas phase Beckmann rearrangement reaction.
In order to further improve the energy utilization efficiency, the tube array reactor is preferably provided with the catalyst filled in the tube array, the inner diameter of the tube array is 10-28mm, and the length-diameter ratio is 50-500, so that the heat released by the gas-phase Beckmann rearrangement reaction in the tube array can be fully dissipated through the tube array, the carrier gas containing cyclohexanone oxime between the shell side and the tube array is heated, the energy is further fully utilized, and the waste is reduced.
Typically, but not by way of limitation, the reaction temperature for gas phase rearrangement is, for example, 330 ℃, 350 ℃, 380 ℃ or 400 ℃; the inner diameter of the tube in the tube array reactor is, for example, 10mm, 12mm, 15mm, 18mm, 20mm, 22mm, 25mm or 28mm, and the aspect ratio is, for example, 50, 80, 100, 120, 150, 200, 300, 400 or 500.
The advantageous effects of the present application will be further described below with reference to examples and comparative examples.
Example 1
The embodiment provides a caprolactam refining and purifying method, which comprises the following steps:
(1) The cyclohexanone oxime undergoes a gas phase rearrangement reaction in a tube reactor to obtain a reaction solution containing caprolactam, wherein the tube inside diameter of the tube is 20mm, the length-diameter ratio of the tube is 150, and the temperature in the tube side is 380 ℃.
(2) And removing the solvent from the reaction solution containing caprolactam to obtain a crude caprolactam product.
(3) Carrying out negative pressure rectification on the caprolactam crude product, controlling the absolute pressure of rectification to be 0.5kPa, controlling the end gas phase temperature to be 98 ℃, controlling the liquid phase temperature to be 140 ℃, and collecting rectification fractions at different temperatures, wherein a first fraction is collected at 50-70 ℃, a second fraction is collected at 71-95 ℃, and a caprolactam fraction is collected at 96-98 ℃.
(4) Pouring the caprolactam fraction into a sweating crystallizer, cooling to 60 ℃ at a cooling rate of 0.15 ℃/h, and preserving heat for 10 hours to obtain a caprolactam crystallization material;
(5) Heating the caprolactam crystal material to sweat at a heating rate of 0.15 ℃/h, extracting a third fraction at a first sweat-generating temperature of 63 ℃, extracting a fourth fraction at a second sweat-generating temperature of 68.8 ℃, and obtaining the rest material, namely a caprolactam product.
Example 2
This example provides a process for refining and purifying caprolactam, which differs from example 1 in that the absolute pressure of the negative pressure rectification in step (3) is 0.1kPa, the final gas phase temperature is 96 ℃, and the caprolactam fraction is collected at 94-96 ℃.
Example 3
This example provides a process for purifying caprolactam, which is different from example 1 in that in step (3), the absolute pressure of negative pressure distillation is 1kPa, the final gas phase temperature is 110 ℃, and the caprolactam fraction is collected at 96-110 ℃.
Example 4
This example provides a method for purifying caprolactam, which is different from example 1 in that in step (3), the absolute pressure of negative pressure distillation is 0.5kPa, the final gas phase temperature is 105 ℃, and the caprolactam fraction is collected at 96-105 ℃.
Example 5
This example provides a process for refining caprolactam which differs from example 1 in that in step (4) the temperature is reduced to 30℃and then the temperature is maintained.
Example 6
This example provides a process for refining and purifying caprolactam, which differs from example 1 in that in step (4), the cooling rate is 0.5 ℃/h.
Example 7
This example provides a process for refining and purifying caprolactam, which differs from example 1 in that in step (4), the cooling rate is 1 ℃/h.
Example 8
This example provides a process for refining caprolactam which differs from example 1 in that in step (5) the rate of temperature increase is 0.5 ℃/h.
Example 9
This example provides a process for refining caprolactam which differs from example 1 in that in step (5) the rate of temperature increase is 1 ℃/h.
Example 10
This example provides a process for refining caprolactam which differs from example 1 in that in step (4) the incubation time is 5 hours.
Example 11
This example provides a process for refining caprolactam which differs from example 1 in that in step (4) the incubation time is 1h.
Example 12
This example provides a process for the purification of caprolactam which differs from example 1 in that in step (5) a third fraction is taken at a first sweating temperature of 60℃and a fourth fraction is taken at a second sweating temperature of 68.9 ℃.
Example 13
This example provides a process for the purification of caprolactam which differs from example 1 in that in step (5) a third fraction is taken at a first sweating temperature of 65℃and a fourth fraction is taken at a second sweating temperature of 66 ℃.
Example 14
This example provides a process for refining and purifying caprolactam, which differs from example 1 in that in step (5), the fourth fraction is withdrawn with the second sweating temperature set at 69.3 ℃.
Example 15
This example provides a process for refining and purifying caprolactam, which differs from example 1 in that in step (5), the third fraction is withdrawn with the first sweat-generating temperature set at 55 ℃.
Example 16
This example provides a process for refining caprolactam which differs from example 1 in that in step (4) the incubation time is 0.5h.
Example 17
This example provides a process for refining caprolactam which differs from example 1 in that in step (4) the incubation time is 15 hours.
Example 18
This example provides a process for refining and purifying caprolactam, which differs from example 1 in that in step (4), the cooling rate is 0.05 ℃/h.
Example 19
This example provides a process for refining and purifying caprolactam, which differs from example 1 in that in step (4), the cooling rate is 2 ℃/h.
Example 20
This example provides a process for refining caprolactam which differs from example 1 in that in step (5) the rate of temperature increase is 0.05 ℃/h.
Example 21
This example provides a process for refining caprolactam which differs from example 1 in that in step (5) the heating rate is 2 ℃/h.
Example 22
This example provides a process for refining and purifying caprolactam, which differs from example 1 in that in step (4), the cooling crystallization temperature is 25 ℃.
Example 23
This example provides a process for refining caprolactam which differs from example 1 in that in step (4) the cooling crystallization temperature is 68 ℃.
Example 24
This example provides a process for refining caprolactam which differs from example 1 in that in step (3) the absolute pressure of the rectification is 0.05kPa.
Example 25
This example provides a process for refining caprolactam which differs from example 1 in that in step (3) the absolute pressure of the rectification is 2kPa.
Comparative example 1
This comparative example provides a process for refining and purifying caprolactam, which differs from example 1 in that in step (3) the first fraction is not collected and the second fraction is collected directly at the second rectification temperature of 71-95 ℃.
Comparative example 2
This comparative example provides a process for the purification of caprolactam by purification which differs from example 1 in that the caprolactam fraction is collected at 111-115 ℃.
Comparative example 3
This comparative example provides a method for refining and purifying caprolactam, which is different from example 1 in that step (5) is not performed, and the material obtained by cooling and crystallizing step (4) is used as caprolactam product.
Comparative example 4
This comparative example provides a method for refining and purifying caprolactam, which is different from example 1 in that step (4) and step (5) are not performed, and the caprolactam fraction obtained in step (3) is used as a caprolactam product.
Test examples
Caprolactam content detection is carried out on caprolactam fractions obtained in the preparation processes of the above examples and the comparative examples, and caprolactam content, yield, potassium permanganate absorption and volatile base content are respectively detected on caprolactam products obtained in each example and comparative example, and the results are shown in the following table 1. The caprolactam content is detected by adopting a gas chromatography method, the potassium permanganate absorption value is detected according to GB/T13255.3, and the volatile alkali content is detected according to GB/T13255.4.
TABLE 1
Note that: the potassium permanganate value of the caprolactam superior product is less than or equal to 4, and the volatile alkali content is less than 0.4mmol/kg.
From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects: the first fraction and the second fraction are removed by controlling different distillation temperatures in the negative pressure rectification process, the caprolactam fraction is cooled and crystallized to obtain a caprolactam crystallization material, and finally the caprolactam crystallization material is subjected to sweating, so that the residual material is collected by removing sweat to obtain a high-purity caprolactam product, and meanwhile, the whole process does not adopt a solvent, so that the method is more environment-friendly and safer, and the refining cost of caprolactam is effectively saved.
Example 26
The embodiment provides a caprolactam refining and purifying method, which is different from embodiment 1 in that the second fraction and the third fraction collected in embodiment 1 are returned to step (3) to continue negative pressure rectification, the fourth fraction is collected to return to step (4) to continue cooling crystallization, and the steps are circularly performed four times, and the purity, potassium permanganate absorption value and organic alkali content and yield of the caprolactam product are detected again, so that the result shows that the purity, potassium permanganate absorption value and volatile alkali content of the caprolactam product are the same as those of embodiment 1, and the yield is 98.28%, which indicates that the recovery of the second fraction, the third fraction and the fourth fraction can obviously improve the yield of the caprolactam product under the condition that the purity and the performance index of the caprolactam product are the same. The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (4)
1. A method for refining and purifying caprolactam, characterized in that the method comprises the following steps:
Step S1, carrying out negative pressure rectification on a caprolactam crude product, collecting a first fraction at a first rectification temperature, collecting a second fraction at a second rectification temperature, and collecting a caprolactam fraction at a third rectification temperature, wherein the first rectification temperature is 50-70 ℃, the second rectification temperature is 71-95 ℃, and the third rectification temperature is 96-110 ℃;
s2, cooling and crystallizing the caprolactam fraction to obtain a caprolactam crystallization material;
s3, sweating the caprolactam crystal material, removing sweat, and collecting the rest material to obtain a caprolactam product;
in the step S1, the pressure of the negative pressure rectification is 0.1-1kPa;
the step S3 includes: sweating the caprolactam crystal material, collecting a third fraction at a first sweating temperature, and collecting a fourth fraction at a second sweating temperature, wherein the first sweating temperature is 60-65 ℃, and the second sweating temperature is 66-68.9 ℃;
in the step S2, the temperature of cooling crystallization is 30-60 ℃, and the heat preservation time is 1-10h;
S2, reducing the caprolactam fraction to a crystallization temperature in a gradient cooling mode, wherein the gradient cooling rate is 0.15-1 ℃/h;
Heating the caprolactam crystal material to a sweating temperature in a gradient heating mode, wherein the gradient heating rate is 0.15-1 ℃/h;
the second fraction and/or the third fraction is returned to the step S1 for negative pressure rectification;
the fourth fraction returns to the step S2 for cooling crystallization;
The crude caprolactam is obtained by removing the solvent from a reaction solution prepared by vapor phase rearrangement of cyclohexanone oxime.
2. The refining and purifying method according to claim 1, wherein in the step S1, the pressure of the negative pressure rectification is 0.4 to 0.6kPa.
3. The refining purification method according to claim 1, wherein the gas phase rearrangement is performed in a tube array reactor, and the reaction temperature of the gas phase rearrangement is 330 to 400 ℃.
4. The purification method according to claim 3, wherein the tube array reactor is filled with a catalyst, and the tube array has an inner diameter of 10 to 28mm and an aspect ratio of 50 to 500.
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| US4457807A (en) * | 1981-05-09 | 1984-07-03 | Stamicarbon B.V. | Process for the purification of ε-caprolactam |
| CN108658863A (en) * | 2018-04-24 | 2018-10-16 | 河北美邦工程科技股份有限公司 | A method of purifying caprolactam using fused junction crystallization |
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| IT1113404B (en) * | 1979-02-28 | 1986-01-20 | Snia Viscosa | INTERNATIONAL PATENTS S.R.L. VIA BRENTANO 2 MILAN |
| FR2809395B1 (en) * | 2000-05-26 | 2002-07-19 | Rhodia Polyamide Intermediates | LACTAM PURIFICATION PROCESS |
| CN101429148B (en) * | 2007-11-08 | 2012-08-29 | 中国石油化工股份有限公司 | Process for production of Epsilon-hexanolactam |
| US8841445B2 (en) * | 2012-12-19 | 2014-09-23 | Basf Se | Process for preparing purified caprolactam from the Beckmann rearrangement of cyclohexane oxime |
| CN109721537B (en) * | 2017-10-30 | 2021-01-08 | 中国石油化工股份有限公司 | Refining method of caprolactam |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| US4457807A (en) * | 1981-05-09 | 1984-07-03 | Stamicarbon B.V. | Process for the purification of ε-caprolactam |
| CN108658863A (en) * | 2018-04-24 | 2018-10-16 | 河北美邦工程科技股份有限公司 | A method of purifying caprolactam using fused junction crystallization |
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