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Process for continuous purification of crude epsi-caprolactam

A technology of caprolactam and purification method, which is applied in the field of crude ε-caprolactam purification and can solve problems such as inability to purify

Inactive Publication Date: 2003-12-24
INVISTA TECHNOLOG IES S A R L +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0006] The disadvantage of the process in US-A-5,496,941 is the preparation by cyclization of alkyl 6-aminocaproate, 6-aminocapronitrile, 6-aminocaproic acid, 6-aminocaproamide and / or oligomers thereof Crude ε-caprolactam, as described in WO-A-9837063, cannot be efficiently purified by this method
[0007] We have found that this is caused by the fact that ε-caprolactams prepared by cyclization contain small amounts of N-substituted or C-substituted lactams and / or amides and that they cannot be effectively remove

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment I

[0030] 73.6 g of crude ε-caprolactam were obtained by cyclization of mixtures of 6-aminocaproic acid, 6-aminocaproamide and its oligomers and some other caprolactams at 300°C as described in WO-A-9837063 Example IX . The crude ε-caprolactam contained impurities such as 6345 ppm N-methylcaprolactam, 100 ppm methyl-valerolactam and 78 ppm valeramide, and was purified by melt crystallization according to the following procedure.

[0031] Water was added to the crude caprolactam to obtain a mixture containing 10% by weight of water. The mixture was heated to 50°C to obtain a homogeneous melt. The temperature was then slowly lowered to 30°C at a rate of about 10°C per hour under mechanical stirring. A slurry of caprolactam crystals formed during cooling. When the temperature reached 30°C, the crystals were separated by filtration and then washed 2-3 times with saturated aqueous caprolactam solution.

[0032] 33.7 g of pure caprolactam crystals were obtained, containing 51 ppm o...

Embodiment II

[0035] The product of Example I was recrystallized by the same procedure. The product contained 2 ppm N-methylcaprolactam, 1 ppm methyl-valerolactam and <1 ppm valeramide. E290 is 0.02, VB<0.4meq / kg. This example shows that pure caprolactam obtained by two crystallization steps meets the VB specification for caprolactam obtained by Beckmann rearrangement.

Embodiment III

[0037] Example I was repeated, except that light and heavy fractions were removed from crude caprolactam by distillation on a short Vigreux column before crystallization. 45.7 g of distilled caprolactam containing 2121 ppm N-methylcaprolactam, 85 ppm methyl-valerolactam and 69 ppm valeramide were crystallized. After crystallization, 23.8 g of pure caprolactam crystals were obtained, which contained 39 ppm of N-methylcaprolactam, 1 ppm of methyl-valerolactam and 2 ppm of valeramide. Introducing a distillation step prior to crystallization resulted in a further increase in E(290) to 0.05 and VB to 0.41 meq / kg compared to a single crystallization step, and yielded a product meeting E290 and VB specifications.

[0038] Comparative experiment A

[0039] Crude caprolactam was purified by sequential extraction with 4-methyl-2-pentanol as described in WO-A-9817642 Example II. The purified caprolactam was isolated by distilling off the 4-methyl-2-pentanol solvent from the obtained ...

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PUM

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Abstract

The invention relates to a process for the purification of crude epsilon -caprolactam, wherein crude epsilon -caprolactam prepared by cyclization of alkyl 6-aminocaproate, 6-aminocapronitrile, 6-aminocaproic acid, 6 aminocaproic amide and / or oligomers thereof, is subjected to a crystallization process.

Description

technical field [0001] The present invention relates to a process for the purification of crude ε-caprolactam. Background technique [0002] Such a method is known from US-A-5,496,941. This patent document describes the continuous purification of crude ε-caprolactam by hydrogenation followed by work-up in an acidic medium and subsequent distillation in an alkaline medium. Treatment in acid media can be carried out in two ways: [0003] (1) The hydrogenation product is passed through an ion exchanger containing terminal acid groups in a solvent, or [0004] (2) In the presence of sulfuric acid, the hydrogenation product is distilled. [0005] The process yields a processed product from which impurities such as cyclic nitriles, amines and imines have been removed. [0006] The disadvantage of the process in US-A-5,496,941 is the preparation by cyclization of alkyl 6-aminocaproate, 6-aminocapronitrile, 6-aminocaproic acid, 6-aminocaproamide and / or o...

Claims

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Application Information

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IPC IPC(8): C07D201/08C07D201/16
CPCC07D201/16C07D201/08
Inventor F·P·W·阿格特博格R·P·M·圭特N·F·哈尔森
Owner INVISTA TECHNOLOG IES S A R L
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