CN110683989A - Heterogeneous rearrangement method for preparing caprolactam from cyclohexanone oxime - Google Patents
Heterogeneous rearrangement method for preparing caprolactam from cyclohexanone oxime Download PDFInfo
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- CN110683989A CN110683989A CN201910972363.4A CN201910972363A CN110683989A CN 110683989 A CN110683989 A CN 110683989A CN 201910972363 A CN201910972363 A CN 201910972363A CN 110683989 A CN110683989 A CN 110683989A
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- 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
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- C07D201/00—Preparation, separation, purification or stabilisation of unsubstituted lactams
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- C07D201/04—Preparation of lactams from or via oximes by Beckmann rearrangement
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Abstract
The invention belongs to the technical field of chemical reaction engineering, and particularly relates to a heterogeneous rearrangement method for preparing caprolactam from cyclohexanone oxime, which comprises the following steps: dissolving cyclohexanone oxime in a recycled inert solvent to form an inert solvent solution of the cyclohexanone oxime, reacting the inert solvent solution with a recycled acid phase containing caprolactam and oleum in a rearrangement reactor, separating the reacted acid phase into an inert solvent phase and an acid phase through a phase separator, mixing a part of the acid phase with the oleum before circulating to the rearrangement reactor, then entering the rearrangement reactor, and discharging the other part of the acid phase at a corresponding inflow speed of an inlet raw material; for the inert solvent phase, the inert solvent solution used for preparing cyclohexanone oxime is circulated. The method of the invention can greatly improve the reaction rate and selectivity and reduce the energy consumption of the process.
Description
Technical Field
The invention belongs to the technical field of chemical reaction engineering, and particularly relates to a heterogeneous rearrangement method for preparing caprolactam from cyclohexanone oxime.
Background
Caprolactam, the scientific name of epsilon-caprolactam, is an important organic chemical raw material and is mainly used for producing nylon 6 fiber (nylon 6) and nylon 6 engineering plastics. Wherein: the nylon-6 fiber is widely applied to industries such as wool spinning, knitting, weaving, carpet and the like, and the nylon-6 engineering plastic is widely applied to industries such as electronics, automobiles, packaging films and the like. In 2018, the caprolactam consumption in China reaches 301 ten thousand tons, the domestic yield is 284 ten thousand tons, and the self-sufficiency rate is 94%; the domestic capacity is 379 ten thousand tons, the operating rate is only 74.9 percent, the enterprise competition is intense, and the production cost needs to be reduced urgently.
The conversion of cyclohexanone oxime to caprolactam via a liquid phase beckmann rearrangement reaction is currently a widely used technique in industry, and the caprolactam produced by this method accounts for 90% of the world caprolactam production. Fuming sulfuric acid is generally used as a catalyst and a solvent in an industrial process, the selectivity of the reaction is 98.5 percent, but because the reaction system has large heat release and high viscosity, a method of mother liquor circulation is generally adopted in the industrial process, and a cooler is added in the external circulation process to reduce the reaction temperature. In order to enhance the mixing effect, the circulation ratio is generally more than 90 and can reach more than 200 at most, thereby bringing huge energy consumption and material consumption. Therefore, accelerating the reaction heat removal and enhancing mixing performance are potential solutions to this problem.
In order to remove the heat of reaction and control the reaction temperature, patent document 1 proposes a method of vaporizing endothermic heat in the course of the reaction using a low boiling point inert solvent. Further, patent document 2 proposes a method of recycling a mother liquor, absorbing heat by vaporization of a small amount of an inert solvent during the reaction, and recovering the solvent by evaporation during the aging. The heat exchange technology is mainly realized by a vaporization mode in the reaction process, but the vaporization mode has the problems of unstable process, high operation difficulty and the like, and is not beneficial to industrial amplification. Patent document 3CN109503484 uses a high boiling point inert solvent to carry out the reaction, but the heat transfer efficiency is low and the amount of reaction impurities is large even when only the inert solvent is used for heat transfer. Thus, existing processes still fail to meet the need to solve existing problems.
Documents of the prior art
Patent document
Patent document 1: US4257950
Patent document 2: CN101851203
Patent document 3: CN109503484
Disclosure of Invention
Technical problem to be solved by the invention
The invention aims to provide a heterogeneous rearrangement method for preparing caprolactam from cyclohexanone oxime, which adopts an inert solvent as a solvent of the cyclohexanone oxime and a heat absorbent in the reaction process and adopts a method of partial acid phase circulation, so that the reaction rate and selectivity can be greatly improved, and the energy consumption of the process can be reduced.
Means for solving the technical problem
In view of the above problems, the present invention provides a heterogeneous rearrangement process for preparing caprolactam from cyclohexanone oxime, comprising the steps of: dissolving cyclohexanone oxime in a recycled inert solvent to form an inert solvent solution of the cyclohexanone oxime, reacting the inert solvent solution with a recycled acid phase containing caprolactam and oleum in a rearrangement reactor, separating the reacted acid phase into an inert solvent phase and an acid phase through a phase separator, mixing a part of the acid phase with the oleum before circulating to the rearrangement reactor, then entering the rearrangement reactor, and discharging the other part of the acid phase at a corresponding inflow speed of an inlet raw material; for the inert solvent phase, the inert solvent solution used for preparing cyclohexanone oxime is circulated.
In one embodiment, the inert solvent is selected from alkanes, cycloalkanes, halogenated hydrocarbons or mixtures thereof having a boiling point in the range of 100 ℃ to 150 ℃ which do not react with oleum.
In one embodiment, the concentration of cyclohexanone oxime in the solution is 1% to 20% by mass.
In one embodiment, the sulfur trioxide in the oleum is present in an amount of 0% to 30% by mass.
In one embodiment, the rearrangement reactor includes, but is not limited to, a stirred reactor, a microreactor with a micromesh structure, and a static mixer.
In one embodiment, the acid phase is a mixture of primarily oleum and reaction product caprolactam, containing small amounts of reactants and reaction impurities.
In one embodiment, the two streams entering the rearrangement reactor have a temperature of 60 ℃ to 130 ℃ and the phase separator has a temperature of 80 ℃ to 150 ℃, and the pressure in the rearrangement reactor and the phase separator should be higher than the saturated vapor pressure of the inert solvent at the respective temperatures.
In one embodiment, the total residence time of the reaction solution in the rearrangement reactor and the phase separator is from 1min to 60 min.
In one embodiment, the recycle ratio is from 0.1 to 40, where recycle ratio refers to the mass ratio of the acid phase recycled to the rearrangement reactor to the acid phase withdrawn.
In one embodiment, the molar flow rate ratio of oleum to cyclohexanone oxime charged to the circulating reaction system is in the range of 0.8 to 1.5.
The invention has the advantages of
(1) The inert solvent is used for carrying reactants, so that the reaction temperature rise can be effectively reduced, the control on the reaction process is favorably enhanced, and the reaction selectivity is improved;
(2) the method of acid phase circulation can further control the reaction temperature rise, adjust the physical and chemical properties of the reaction system and is beneficial to the reaction process;
(3) the method adopts low circulation ratio and phase separation, has strong operability and greatly reduces the energy consumption compared with the prior process.
Further features of the present invention will become apparent from the following description of exemplary embodiments.
Drawings
FIG. 1 is a schematic view of a reaction system of the present invention.
Illustration of the drawings:
i: a cyclohexanone oxime batching tank; II: a mixing reactor; III: a phase splitter;
1-cyclohexanone oxime; 2-cyclohexanone oxime in an inert solvent; 3-reaction liquid; 4-the acid phase of the cycle; 5-recycle of inert solvent; 6-removal of the downstream acid phase; 7-oleum.
Detailed Description
One embodiment of the present disclosure will be specifically described below, but the present disclosure is not limited thereto.
The heterogeneous rearrangement method for preparing caprolactam from cyclohexanone oxime provided by the invention is characterized in that the cyclohexanone oxime is dissolved in a recycled inert solvent, and reacts with a recycled acid phase containing caprolactam and fuming sulfuric acid in a rearrangement reactor, and the reacted solution is divided into an inert solvent phase and an acid phase through a phase separator. Wherein, for the acid phase, one part of the acid phase is mixed with fresh fuming sulfuric acid before being circulated to the reactor and then enters the rearrangement reactor, and the other part of the acid phase flows out of the system at the corresponding inflow speed of the inlet raw material and then goes downstream for subsequent reaction or treatment; and for the inert solvent phase, circulating the inert solvent phase to a dosing tank to prepare the inert solvent solution of cyclohexanone oxime.
The inert solvent is alkane, cycloalkane, halogenated hydrocarbon or their mixture which does not react with oleum and has a boiling point of 100-150 ℃, and includes but is not limited to: n-paraffin with 8-15 carbon atoms or their mixture, and D80 and D100 # solvated oil. The mass percent concentration of cyclohexanone oxime in the inert solvent solution of cyclohexanone oxime is 1% -20%. The oleum accounts for 0 to 30 percent of the mass fraction of sulfur trioxide in the oleum.
The mixing reactor can realize good mixing effect of two materials, including but not limited to a stirring reactor, a micro-reactor with a micro-sieve pore structure and a static mixer.
The temperature of the two streams entering the mixing reactor is 60-120 ℃, the temperature of the phase separator is 70-140 ℃, and the pressure of the reactor and the phase separator is higher than the saturated vapor pressure of the inert solvent at the corresponding temperature, namely, the inert solvent is ensured not to be vaporized. The total residence time of the reaction solution in the reactor and the phase separator is 1-60 min.
The recycle ratio of the reaction system is 0.1-40, wherein the recycle ratio refers to the mass ratio of the acid phase recycled to the reactor to the acid phase flowing out of the system for downstream reaction or treatment. The molar flow rate ratio of oleum and cyclohexanone oxime fed into the circulating reaction system is 0.8-1.5, wherein oleum refers to the sum of the molar flow rates of sulfuric acid and sulfur trioxide.
The invention can realize the preparation of caprolactam by a circulating reaction system consisting of a cyclohexanone oxime batching tank I, a mixing reactor II and a phase separator III, as shown in figure 1. The basic features of the invention are: (1) the inert solvent is used as a solvent of the raw material cyclohexanone oxime and a heat absorbent in the reaction process, so that the temperature rise in the reaction process is reduced; (2) the inert solvent is not vaporized in the reaction process, and the inert solvent and the acid phase are separated by a phase separator; (3) part of acid phase and fuming sulfuric acid are mixed and then are circulated to a mixing reactor to be mixed and reacted with the inert solvent solution of cyclohexanone oxime, and the circulation ratio of the catalyst can be greatly reduced compared with that of the existing industrial process; (4) preheating the inert solvent solution of cyclohexanone oxime and the circulating fuming sulfuric acid and reacted acid phase mixed solution to a certain temperature, and then mixing in a mixing reactor; (5) the mixing reactor is to provide sufficient mixing performance for the two phases and may be a stirred reactor, a micro-reactor with a micro-mesh structure, a static mixer, or the like.
Example 1
An experiment was carried out according to the process of the invention with 12.5kg/h of a n-decane solution of cyclohexanone oxime (2) having a mass fraction of cyclohexanone oxime of 8%, mixed in a microreactor (II) with a mixture of 1kg/h of 10% oleum (7) and 2kg/h of a circulating acid phase (4) at an inlet temperature of 80 ℃ into a phase separator for phase separation at a temperature of 100 ℃. The reaction acid-oxime ratio (i.e. the molar ratio of the added oleum to the cyclohexanone oxime) was 1.2, the circulation ratio was 1, and the total reaction residence time was 30 min. The reaction conversion rate is more than 99.9%, and the selectivity is more than 99.5%.
Example 2
According to the method of the invention, 20kg/h of a D80 solution (2) of cyclohexanone oxime with a mass fraction of 5% cyclohexanone oxime was mixed with a mixture of 1kg/h of 20% oleum (7) and 1kg/h of a circulating acid phase (4) in a stirred reactor (II) at an inlet temperature of 60 ℃ and phase separation in a phase separator at a temperature of 100 ℃. The reaction acid-oxime ratio (i.e. the molar ratio of the added oleum to the cyclohexanone oxime) was 1.2, the circulation ratio was 0.5, and the total reaction residence time was 20 min. The reaction conversion rate is more than 99.9%, and the selectivity is more than 99.6%.
Example 3
An experiment was carried out according to the process of the invention with 12.5kg/h of an n-octane solution (2) of cyclohexanone oxime having a mass fraction of 8% cyclohexanone oxime mixed in a microreactor (II) with an inlet temperature of 80 ℃ with a mixture of 1.2kg/h of 20% oleum (7) and 10kg/h of a circulating acid phase (4) and entering a phase separator for phase separation at a temperature of 100 ℃. The reaction acid-oxime ratio (i.e. the molar ratio of the added oleum to the cyclohexanone oxime) was 1.4, the circulation ratio was 5, and the total reaction residence time was 30 min. The reaction conversion rate is more than 99.9%, and the selectivity is more than 99.8%.
Industrial applicability
The heterogeneous rearrangement method for preparing caprolactam from cyclohexanone oxime provided by the invention can greatly improve the reaction rate and selectivity, reduce the process energy consumption and has good industrial application prospect.
The present invention is not limited to the above embodiments, and any changes or substitutions that can be easily made by those skilled in the art within the technical scope of the present invention are also within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (10)
1. A heterogeneous rearrangement process for preparing caprolactam from cyclohexanone oxime, comprising the steps of: dissolving cyclohexanone oxime in a recycled inert solvent to form an inert solvent solution of the cyclohexanone oxime, reacting the inert solvent solution with a recycled acid phase containing caprolactam and oleum in a rearrangement reactor, separating the reacted acid phase into an inert solvent phase and an acid phase through a phase separator, mixing a part of the acid phase with the oleum before circulating to the rearrangement reactor, then entering the rearrangement reactor, and discharging the other part of the acid phase at a corresponding inflow speed of an inlet raw material; for the inert solvent phase, the inert solvent solution used for preparing cyclohexanone oxime is circulated.
2. The process according to claim 1, wherein the inert solvent is selected from alkanes, cycloalkanes, halogenated hydrocarbons or mixtures thereof having a boiling point of between 100 ℃ and 150 ℃, which do not react with oleum.
3. The method according to claim 1, wherein the concentration of cyclohexanone oxime in the solution is 1-20% by mass.
4. The process according to claim 1, wherein the sulfur trioxide in the oleum is present in a mass fraction of 0% to 30%.
5. The process of claim 1, wherein the rearrangement reactor includes but is not limited to a stirred reactor, a micro reactor with a micro mesh structure, a static mixer.
6. The process of claim 1 wherein the acid phase is predominantly a mixture of oleum and reaction product caprolactam comprising minor amounts of reactants and reaction impurities.
7. The process according to claim 1, wherein the two flows entering the rearrangement reactor have a temperature of 60 ℃ to 130 ℃, the temperature of the phase separator has a temperature of 80 ℃ to 150 ℃, and the pressure of the rearrangement reactor and the phase separator is higher than the saturated vapor pressure of the inert solvent at the corresponding temperature.
8. The process according to claim 1, wherein the total residence time of the reaction solution in the rearrangement reactor and the phase separator is from 1min to 60 min.
9. The process according to claim 1, wherein the recycle ratio is from 0.1 to 40, wherein the recycle ratio refers to the mass ratio of the acid phase recycled to the rearrangement reactor to the acid phase withdrawn.
10. The process according to claim 1, wherein the molar flow ratio of oleum to cyclohexanone oxime charged to the circulating reaction system is 0.8-1.5.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113121397A (en) * | 2021-04-20 | 2021-07-16 | 中国石油化工股份有限公司 | Method for preparing caprolactam from cyclohexanone oxime |
| WO2024000848A1 (en) * | 2022-06-29 | 2024-01-04 | 中国天辰工程有限公司 | Caprolactam synthesis method free of by-production of ammonium sulfate |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4257950A (en) * | 1978-10-16 | 1981-03-24 | Basf Aktiengesellschaft | Continuous preparation of ε-caprolactam by Beckmann rearrangement |
| CN1508128A (en) * | 2002-12-13 | 2004-06-30 | 中国石油化工股份有限公司巴陵分公司 | Method for preparing caprolactam |
| CN101851203A (en) * | 2010-03-03 | 2010-10-06 | 湘潭大学 | Method for continuously preparing hexanolactam by using cyclohexanone-oxime Beckmann rearrangement reaction |
| CN109503484A (en) * | 2018-12-29 | 2019-03-22 | 清华大学 | A method of caprolactam is prepared using higher boiling atent solvent |
-
2019
- 2019-10-14 CN CN201910972363.4A patent/CN110683989A/en active Pending
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4257950A (en) * | 1978-10-16 | 1981-03-24 | Basf Aktiengesellschaft | Continuous preparation of ε-caprolactam by Beckmann rearrangement |
| CN1508128A (en) * | 2002-12-13 | 2004-06-30 | 中国石油化工股份有限公司巴陵分公司 | Method for preparing caprolactam |
| CN101851203A (en) * | 2010-03-03 | 2010-10-06 | 湘潭大学 | Method for continuously preparing hexanolactam by using cyclohexanone-oxime Beckmann rearrangement reaction |
| CN109503484A (en) * | 2018-12-29 | 2019-03-22 | 清华大学 | A method of caprolactam is prepared using higher boiling atent solvent |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113121397A (en) * | 2021-04-20 | 2021-07-16 | 中国石油化工股份有限公司 | Method for preparing caprolactam from cyclohexanone oxime |
| WO2024000848A1 (en) * | 2022-06-29 | 2024-01-04 | 中国天辰工程有限公司 | Caprolactam synthesis method free of by-production of ammonium sulfate |
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Application publication date: 20200114 |