CN110615752A - Method for preparing caprolactam through Beckmann rearrangement catalyzed by ionic liquid - Google Patents
Method for preparing caprolactam through Beckmann rearrangement catalyzed by ionic liquid Download PDFInfo
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- CN110615752A CN110615752A CN201911077187.4A CN201911077187A CN110615752A CN 110615752 A CN110615752 A CN 110615752A CN 201911077187 A CN201911077187 A CN 201911077187A CN 110615752 A CN110615752 A CN 110615752A
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07D—HETEROCYCLIC COMPOUNDS
- C07D201/00—Preparation, separation, purification or stabilisation of unsubstituted lactams
- C07D201/02—Preparation of lactams
- C07D201/04—Preparation of lactams from or via oximes by Beckmann rearrangement
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- 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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Abstract
The invention provides a method for preparing caprolactam by Beckmann rearrangement under the catalysis of ionic liquid, which comprises the following steps: (1) adding acid A and acid B into a solvent for dissolving; (2) adding cyclohexanone oxime into the solution obtained in the step (1) for dissolving; (3) and (3) enabling the solution obtained in the step (2) to pass through a tubular reactor at a certain flow rate to obtain a caprolactam product. The method solves the problem of by-product ammonium sulfate in the process of producing caprolactam by a sulfuric acid method, and has the advantages of simple operation method, mild reaction conditions, high reaction rate and less by-products.
Description
Technical Field
The invention belongs to the field of chemical catalysts, and particularly relates to a method for preparing caprolactam through Beckmann rearrangement catalyzed by ionic liquid.
Background
Caprolactam is an important chemical raw material and an important monomer for synthesizing polymers such as nylon and the like. Caprolactam is mainly prepared by the Beckmann rearrangement reaction of cyclohexanone oxime raw materials. The beckmann rearrangement reaction is a rearrangement reaction catalyzed by acid, and the reactant cyclohexanone oxime is rearranged into caprolactam under the catalysis of the acid. Acids capable of catalyzing Beckmann rearrangement include acetic acid, hydrochloric acid and acetic anhydride, sulfuric acid and solid acid, and under the action of the acids, cyclohexanone oxime quickly undergoes rearrangement reaction to generate caprolactam and emit heat. Currently, the industrial synthesis of caprolactam is mainly that under the action of concentrated sulfuric acid or oleum, cyclohexanone oxime undergoes a rearrangement reaction to generate caprolactam. However, the produced caprolactam and sulfuric acid are closely chemisorbed and cannot be separated by a common method such as fractional distillation, extraction, etc. In industrial production, ammonia is generally used to neutralize the acid in the reaction system to produce ammonium sulfate which can be separated from caprolactam. The reaction technology is mature, but a large amount of ammonium sulfate is produced as a byproduct, and the price of the ammonium sulfate is low, so that the economic benefit is reduced.
In view of the huge cost problem caused by sulfuric acid catalysis, many acidic catalysts for beckmann rearrangement have been studied, aiming to obtain good catalytic effect without using sulfuric acid, so as to reduce the production cost of caprolactam. Through research on acidic substances, people find that substances such as strong acid type ion exchange resin, strong acid molecular sieve, ionic liquid, organic strong acid and the like can catalyze Beckmann rearrangement reaction except sulfuric acid, but the problems of low conversion rate, high impurity content of products and the like cannot be solved.
It is known from literature that acidic ionic liquid has catalytic activity for rearrangement reaction, but the general ionic liquid catalytic rearrangement reaction generates a large amount of side reactions to produce cyclohexanone and other byproducts, which increases the burden of a post-treatment process device and increases the production cost of caprolactam.
Disclosure of Invention
In view of the above, the invention aims to provide a method for preparing caprolactam by beckmann rearrangement under catalysis of ionic liquid, so as to solve the problem of by-product ammonium sulfate in the production of caprolactam by the existing sulfuric acid method, and the method is simple in operation method, mild in reaction conditions, fast in reaction rate and less in by-product.
In order to achieve the purpose, the technical scheme of the invention is realized as follows:
a method for preparing caprolactam by Beckmann rearrangement catalyzed by ionic liquid comprises the following steps:
s1: adding a certain amount of acid A into a solvent for dissolving;
s2: adding a certain amount of acid B into the solution obtained in the step S1 for dissolution;
s3: adding cyclohexanone oxime to the solution obtained in step S2 to dissolve;
s4: the solution obtained in step S3 was passed through a tubular reactor with a certain residence time.
In the above step, the acid A is Lewis acid, and the acid B is organic strong acid.
According to the invention, Lewis acid-organic strong acid ionic liquid is adopted as a catalyst, in the reaction process, Beckmann rearrangement reaction is firstly carried out on cyclohexanone oxime to generate caprolactam, and the generated caprolactam and the original ionic liquid can form Lewis acid-organic strong acid-caprolactam ternary ionic liquid in situ. The formed ionic liquid has good catalysis effect on Beckmann rearrangement reaction, and meanwhile, the process of forming the ionic liquid has strong induction effect on the conversion of cyclohexanone oxime into caprolactam, and the two driving forces act together to ensure that the cyclohexanone oxime can be quickly and efficiently converted into caprolactam, and the conversion is quick and the selectivity is extremely high.
The product generated by the reaction is Lewis acid-organic strong acid-caprolactam ternary ionic liquid, and caprolactam in the ionic liquid can be separated out by an extraction method without using alkaline substances such as ammonia gas and the like for neutralization, so that the post-treatment process of the product is greatly simplified, and the cost is reduced. The extracted ionic liquid can be used as a catalyst for repeated use, is economical and environment-friendly, and has good economic and social benefits.
The invention provides a method for preparing caprolactam by improving a Beckmann rearrangement reaction catalyzed by an ionic liquid, which successfully avoids using sulfuric acid as a catalyst and further solves the problem of by-product ammonium sulfate in the existing caprolactam production method.
Further, in step S1, the solvent is one or more of methanol, ethanol, acetone, diethyl ether, acetonitrile, ethyl acetate, dimethyl sulfoxide, N-dimethylformamide, and toluene, preferably acetonitrile and toluene. The conditions are helpful for improving the cyclohexanone oxime conversion rate and caprolactam selectivity of the reaction.
Further, in the step S1, the acid a is one or more of ZnCl2, AlCl3, PCl3, FeCl3, and BCl3, preferably ZnCl2 and AlCl3, and the concentration of the acid a is 0.1 to 2000g/L, preferably 800 to 1500 g/L. The conditions are helpful for improving the cyclohexanone oxime conversion rate and caprolactam selectivity of the reaction.
Further, in the step S2, the acid B is one or more of benzenesulfonic acid, sulfamic acid, methanesulfonic acid, p-toluenesulfonic acid, trifluoromethanesulfonic acid, trifluorobenzene sulfonic acid, picric acid, trifluoroacetic acid, trichloroacetic acid, urea, pyridine hydrochloride, and triethylamine hydrochloride, preferably benzenesulfonic acid and p-toluenesulfonic acid, and the concentration of the acid B is 0.1 to 2000g/L, preferably 500 to 750 g/L. The conditions are helpful for improving the cyclohexanone oxime conversion rate and caprolactam selectivity of the reaction.
Further, in the step S3, the concentration of the cyclohexanone oxime is 50-5000 g/L, preferably 2000-3000 g/L. The conditions are helpful for improving the cyclohexanone oxime conversion rate and caprolactam selectivity of the reaction.
Further, in the step S4, the temperature of the tubular reactor is 60-150 ℃, preferably 80-90 ℃, and the reaction residence time is 1-60 min, preferably 2-5 min. The condition can obviously improve the cyclohexanone-oxime conversion rate and caprolactam selectivity of the reaction.
The method for preparing caprolactam by Beckmann rearrangement under catalysis of the ionic liquid has the following advantages:
(1) the Beckmann rearrangement reaction method provided by the invention has the advantages of higher conversion rate and caprolactam selectivity, and no ammonium sulfate by-product;
(2) the Beckmann rearrangement reaction method provided by the invention has the advantages of short reaction time, mild reaction conditions and post-treatment of products;
(3) the treatment method has simple steps, is easy for industrial amplification and has good application prospect;
(4) the processing method has the advantages of simple raw materials, low price and remarkable cost saving.
Detailed Description
The invention will be described in detail with reference to specific embodiments. The examples are intended to illustrate the invention, but are not intended to limit the scope of applicability of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
In the embodiment of the invention, a method for preparing caprolactam by liquid phase Beckmann rearrangement comprises the following specific steps:
(1) adding 1kg of AlCl3 into 1kg of toluene, and stirring uniformly;
(2) adding 0.5kg of methanesulfonic acid into the solution obtained in the step (1), and stirring the mixture until the mixture is uniform;
(3) adding 2.5kg of cyclohexanone oxime into the solution obtained in the step (2), and stirring until the solution is clear;
(4) enabling the solution obtained in the step (3) to pass through a tubular reactor, wherein the reaction temperature is 90 ℃, and the retention time is 10 min;
(5) the reaction product obtained in step (4) was analyzed by gas chromatography.
The test results are shown in table 1.
Example 2
In the embodiment of the invention, a method for preparing caprolactam by liquid phase Beckmann rearrangement comprises the following specific steps:
(1) adding 1.5kg of ZnCl2 into 1kg of acetonitrile, and stirring uniformly;
(2) adding 0.8kg of p-toluenesulfonic acid into the solution obtained in the step (1), and stirring uniformly;
(3) adding 3kg of cyclohexanone-oxime into the solution obtained in the step (2), and stirring until the solution is clear;
(4) enabling the solution obtained in the step (3) to pass through a tubular reactor, wherein the reaction temperature is 80 ℃, and the retention time is 2 min;
(5) the reaction product obtained in step (4) was analyzed by gas chromatography.
The test results are shown in table 1.
Example 3
In the embodiment of the invention, a method for preparing caprolactam by liquid phase Beckmann rearrangement comprises the following specific steps:
(1) adding 0.8kg of PCl3 into 1kg of dimethyl sulfoxide, and stirring uniformly;
(2) adding 0.5kg of trifluoroacetic acid into the solution obtained in the step (1), and stirring the solution uniformly;
(3) adding 2kg of cyclohexanone oxime into the solution obtained in the step (2), and stirring until the solution is clear;
(4) enabling the solution obtained in the step (3) to pass through a tubular reactor, wherein the reaction temperature is 70 ℃, and the retention time is 5 min;
(5) the reaction product obtained in step (4) was analyzed by gas chromatography.
The test results are shown in table 1.
Example 4
In the embodiment of the invention, a method for preparing caprolactam by liquid phase Beckmann rearrangement comprises the following specific steps:
(1) adding 1.5kg of FeCl3 into 1kg of acetonitrile, and stirring uniformly;
(2) adding 0.8kg of trifluorobenzene sulfonic acid into the solution obtained in the step (1), and stirring the mixture uniformly;
(3) adding 2kg of cyclohexanone oxime into the solution obtained in the step (2), and stirring until the solution is clear;
(4) enabling the solution obtained in the step (3) to pass through a tubular reactor, wherein the reaction temperature is 120 ℃, and the retention time is 5 min;
(5) the reaction product obtained in step (4) was analyzed by gas chromatography.
The test results are shown in table 1.
Comparative example 1
In the embodiment of the invention, a method for preparing caprolactam by liquid phase Beckmann rearrangement comprises the following specific steps:
(1) adding 0.5kg of benzenesulfonic acid into 1kg of toluene, and stirring uniformly;
(2) adding 2kg of cyclohexanone oxime into the solution obtained in the step (1), and stirring until the solution is clear;
(3) enabling the solution obtained in the step (2) to pass through a tubular reactor, wherein the reaction temperature is 100 ℃, and the retention time is 10 min;
(4) the reaction product obtained in step (3) was analyzed by gas chromatography.
The test results are shown in table 1.
Comparative example 2
In the embodiment of the invention, a method for preparing caprolactam by liquid phase Beckmann rearrangement comprises the following specific steps:
(1) adding 1kg of ZnCl2 into 1kg of acetonitrile, and stirring the mixture until the mixture is uniform;
(2) adding 2kg of cyclohexanone oxime into the solution obtained in the step (1), and stirring until the solution is clear;
(3) enabling the solution obtained in the step (2) to pass through a tubular reactor, wherein the reaction temperature is 100 ℃, and the retention time is 10 min;
(4) the reaction product obtained in step (3) was analyzed by gas chromatography.
The test results are shown in table 1.
Table 1: examples and comparative example data
The results of the embodiments of the invention show that the Beckmann rearrangement reaction scheme of cyclohexanone oxime has high reactant conversion, and the reaction product caprolactam has good selectivity.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (6)
1. A method for preparing caprolactam through Beckmann rearrangement catalyzed by ionic liquid is characterized in that the caprolactam is prepared by the following steps:
s1: adding a certain amount of acid A into a solvent for dissolving;
s2: adding a certain amount of acid B into the solution obtained in the step S1 for dissolution;
s3: adding cyclohexanone oxime to the solution obtained in step S2 to dissolve;
s4: the solution obtained in step S3 was passed through a tubular reactor with a certain residence time.
2. The method for preparing caprolactam through Beckmann rearrangement catalyzed by ionic liquid according to claim 1, wherein: in the step S1, the solvent is one or more of methanol, ethanol, acetone, diethyl ether, acetonitrile, ethyl acetate, dimethyl sulfoxide, N-dimethylformamide, and toluene.
3. The method for preparing caprolactam through Beckmann rearrangement catalyzed by ionic liquid according to claim 1 or 2, wherein: in the step S1, the acid A is one or more of ZnCl2, AlCl3, PCl3, FeCl3 and BCl3, and the concentration of the acid A is 0.1-2000 g/L.
4. The method for preparing caprolactam through Beckmann rearrangement catalyzed by ionic liquid according to claim 1, wherein: in the step S2, the acid B is one or more of benzenesulfonic acid, sulfamic acid, methanesulfonic acid, p-toluenesulfonic acid, trifluoromethanesulfonic acid, trifluorobenzene sulfonic acid, picric acid, trifluoroacetic acid, trichloroacetic acid, urea, pyridine hydrochloride and triethylamine hydrochloride, and the concentration of the acid B is 0.1-2000 g/L.
5. The method for preparing caprolactam through Beckmann rearrangement catalyzed by ionic liquid according to claim 1, wherein: in the step S3, the concentration of the cyclohexanone oxime is 50-5000 g/L.
6. The method for preparing caprolactam through Beckmann rearrangement catalyzed by ionic liquid according to claim 1, wherein: in the step S4, the temperature of the tubular reactor is 60-150 ℃, and the reaction residence time is 1-60 min.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113461614A (en) * | 2021-06-30 | 2021-10-01 | 青岛科技大学 | Preparation method of caprolactam |
| CN115608416A (en) * | 2022-10-29 | 2023-01-17 | 神马实业股份有限公司 | Preparation method and application of caprolactam catalyst produced by liquid-phase Beckmann rearrangement |
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| CN102414174A (en) * | 2009-03-04 | 2012-04-11 | 宇部兴产株式会社 | Method for producing amide compound |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113461614A (en) * | 2021-06-30 | 2021-10-01 | 青岛科技大学 | Preparation method of caprolactam |
| CN115608416A (en) * | 2022-10-29 | 2023-01-17 | 神马实业股份有限公司 | Preparation method and application of caprolactam catalyst produced by liquid-phase Beckmann rearrangement |
| CN115608416B (en) * | 2022-10-29 | 2024-04-30 | 神马实业股份有限公司 | Preparation method and application of catalyst for producing caprolactam by liquid-phase Beckmann rearrangement |
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