TW496862B - Recovery of epsi-caprolactam - Google Patents

Abstract

Process to separate ε-caprolactam from 6-aminocaproamide and 6-aminocaproamide oligomers, wherein ε-caprolactam, 6-aminocaproamide and 6-aminocaproamide oligomers are present: in a first aqueous starting mixture, which mixture is contacted with an alcohol extraction solvent, resulting in a first aqueous raffinate phase which is poor in ε-caprolactam and an alcohol phase which is rich in ε-caprolactam and which alcohol phase contains 6-aminocaproamide and/or 6-aminocaproamide oligomers, wherein the latter alcohol phase is subsequently contacted with water (backwash water) resulting in an alcohol extract phase poor in 6-aminocaproamide and/or 6-aminocaproamide oligomers and a second aqueous raffinate phase rich in 6-aminocaproamide and/or 6-aminocaproamide oligomers.

Description

496862 Α7 B7 V. Description of the invention (1) The present invention relates to a method for separating 6-aminohexamidine and 6-aminohexamidine oligomers from ε-caprolactam. This method is known from US-A-5,950,016. This patent application discloses the separation of ε-caprolactam from its nylon-6 oligomer by distillation. The disadvantage of distillation is that ε-caprolactam converts part of it into more oligomers (2% by weight in absolute terms according to US-A-5495016 Example 1). Another disadvantage is that it is present in the distillation residue. Oligomers solidify and block pipelines and other process equipment. The object of the present invention is to provide a method for phase separation of 6-aminohexamidineamine and 6-aminohexamidineamine oligomers from ε-caprolactam, without loss of ε-caprolactam. Printed by the Consumer Cooperatives of the Central Standards Bureau of the Ministry of Economic Affairs--=-· LI: -----, Tt-...... 111 ·· I # (Please read the precautions on the back before filling this page) This The objective is achieved in which ε-caprolactam, 6-aminohexamidine and 6-aminohexamidine oligomers are present in the first aqueous starting mixture, and this mixture is contacted with an alcohol extraction solvent, Resulting in the first aqueous residual phase containing a small amount of ε-caprolactam and the alcohol phase containing a large amount of ε-caprolactam, and in the alcohol phase containing 6-aminohexanamine and / or 6-aminohexanone Ammonium oligomers, in which the alcohol phase is subsequently contacted with water (counter-current water), resulting in alcohol-extracted phases containing a small amount of 6-aminohexamidine and / or 6-aminohexamidine oligomers and a large amount of A second aqueous residual phase of 6-aminohexamidine amine and / or 6-aminohexamidine oligomer. It has been found that the implementation of the method according to the present invention can successfully separate the 6-aminohexamidine amine and 6-aminohexamidine oligomers from the ε-caprolactam phase. EP-Α-729944 reveals ε -hexanox Lentamine can be extracted by the two paper sizes applicable to the Chinese National Standard (CNS) A4 specifications (210 X 297 mm) -4-496862 A7 —____ B7_ by the extraction method. 5. Chloroform, cyclohexane, toluene, Benzene, chloroform, or trichloroethane was recovered from an aqueous mixture that also contained 6-aminohexamidine oligomers. This patent application did not describe the use of an alcohol solvent as an extractant. Effective extraction solvents are exemplified chlorinated solvents, but these solvents are less suitable for environmental reasons. NL-A-6803 152 discloses an example of extracting ε-caprolactam from an aqueous mixture using a C4 -CM ring) aliphatic alcohol. This patent application does not disclose the presence of 6-aminohexamidine or its oligo in an aqueous mixture. Polymer and it was not disclosed that a second extraction with water was performed. The first aqueous starting mixture may also contain 6-aminohexanoic acid and 6-aminohexanoic acid oligomers. This mixture is, for example, a method obtained from EP-A-729944. These compounds were found to be based on In the method of the present invention, it can be effectively separated from ε-caprolactam. This oligomer is usually a dimer and trimer of 6-aminohexanoic acid or 6-aminohexamidine. Higher oligomers may be present at lower levels. The concentration of the oligomer in the first aqueous mixture is preferably higher than 0.5% by weight, and more preferably not higher than 10% by weight. ~ The concentration of ε-caprolactam, 6-aminocaproic acid, 6-aminocaproamide and oligomers in the first aqueous mixture is preferably 5-50% by weight, and more preferably 10- 35% by weight, the concentration of ε-caprolactam is more preferably 5-30% by weight, the concentration of 6-aminohexamidine is more preferably 0.1 to 10% by weight, and the concentration of 6-aminohexanoic acid is more preferably 0.1 to 10% by weight. The alcohol extraction solvent is preferably a solvent that is substantially insoluble in the first aqueous mixture. Here, the term “substantially insoluble” refers to a mixture of an alcohol solvent and an aqueous mixture. -5-Please read the precautions before reading

Printed by the Consumers' Cooperative of the Central Standards Bureau of the Ministry of Economic Affairs 496862 Α7 Β7 V. Description of the invention 0) The two phases that lead to separation at the extraction temperature, in the case of extraction, the mutual solubility is not higher than 30% by weight and preferably lower than 20 weight%. Alcohol extraction solvents are more preferably aliphatic or cycloaliphatic compounds containing one or more hydroxyl groups. The alcohols preferably contain 4 to 12 carbon atoms and more preferably 5 to 8 carbon atoms, more preferably one or two. It is more preferable to have only one hydroxyl group, and it is more suitable to use sterically hindered alcohols. A sterically hindered alcohol is a compound in which the hydroxyl group is bonded to a CWR3 where R1 and R2 are alkyl groups and R3 is an alkyl group or hydrogen, which is beneficial In the method, the obtained aqueous phase is used as a feed for preparing ε-caprolactam, and the hindered alcohols are less likely to react with the N-alkylation product of ε-caprolactam. Printed by the Consumer Cooperatives of the Central Bureau of Standards of the Ministry of Economic Affairs (please read the precautions on the back before filling this page) Examples of compounds containing two hydroxyl groups are hexanediol, nonanediol, neopentyl glycol, and methyl monomethyl propylene glycol , Ethyl monomethyl propylene glycol or butyl monomethyl propylene glycol, examples of compounds containing one hydroxyl group are cyclohexanol, n-butanol, n-pentanol, 2-pentanol, n-hexanol, 4-methyl 2-pentyl Alcohols, 2-ethyl-1-hexanol, 2-propyl-1-heptanol, n-octanol, isononanol, n-decanol, and mixtures of straight and branched C8-alcohols, straight and branched Mixtures of chain C9-alcohols and straight and branched chains. -Alcohol mixtures, the above-mentioned alcohol mixtures can also be used. The preferred alcohols have a high affinity for ε-caprolactone 1 and a boiling point lower than ε-caprolactam, which has a high density difference with water. Commercial supply, low miscibility with water and / or biodegradable. The counter-current water may be pure water or water containing other compounds such as alcohol compounds, and more preferably water having a purity of at least 95% by weight. The first and second aqueous residual liquid phases can be combined into one aqueous mixture for further use. It is more suitable to combine the first aqueous residual liquid phase with the aqueous starting mixture. This preferred embodiment of the method is more suitable for one The paper size in the method device is applicable to the Chinese National Standard (CNS) A4 specification (210 X297 mm) -6-496862 A7 B7 printed by the Consumer Cooperatives of the Central Standards Bureau of the Ministry of Economic Affairs_5. The description of the invention θ) is carried out continuously, this specific implementation The example is characterized in that the extraction is performed in a vertically placed container, wherein the aqueous starting mixture is fed at the middle position of the container, the alcohol extraction solvent is fed to the bottom of the container, and countercurrent water is fed to the top of the container, and the obtained Aqueous residual liquid and alcohol extraction phases were obtained at the bottom and top of the container, respectively. The amount of alcohol extraction solvent and countercurrent water depends on the distribution coefficient of the components to be separated, and those skilled in this phase can easily determine it. The extraction step is performed at a sufficiently high temperature to prevent oligomer precipitation. The extraction temperature may be usually from room temperature to 200 ° C and more preferably from 20 to 170 ° C, and more preferably from 50 to 130 ° C. The pressure during the extraction step is not critical and may be, for example, from about 0.1 MPa to about 2.0 MPa, and more preferably from about 0.1 MPa to about 0.5 MPa, and this pressure must be sufficient to maintain the liquid phase in the extraction process. The extraction can be performed in a conventional extraction apparatus, such as a countercurrent column, a series of mixer settler, a rotating disc mixer, or a pulsed packed tube column. The extraction step preferably produces an alcohol phase containing ε-caprolactam, which may contain 10-40% by weight of 8-caprolactam. After extraction, ε-caprolactam can be recovered from the alcohol phase by known separation methods, such as distillation and extraction. Distillation is more suitable for the use of lower boiling alcohols and any water present in the alcohol phase. Distillation removal from ε-caprolactam, the alcohol solvent and water thus obtained are preferably reused in the method according to the invention. In particular, the present invention relates to the separation of ε-caprolactam from the aqueous mixture obtained below, (I) a method for preparing ε-caprolactam, in which the Chinese National Standard (CNS) 8-4 specification is applied by reacting with water. (210 × 297 mm) 77. &Quot; (Please read the notes on the back before filling in this page) • · _1t

Printed by the Consumers' Cooperative of the Central Standards Bureau of the Ministry of Economic Affairs 496862 A7 ___ ___B7__ 5. Description of the Invention (5) The conversion of 6-aminocapronitrile to crude ε-caprolactam, as disclosed in, for example, US-A-5495016, ( II) Process for the preparation of ε-caprolactam in which 6-aminocaproic acid is cyclized via water, as disclosed in, for example, US-A-4,730,040, or (III) where the starting mixture contains 6-aminocaproic acid And 6-aminohexamidine, as disclosed in, for example, EP-A-729944. The aqueous mixtures obtained from methods (I) and (II) will also contain ammonia gas, which is a by-product of the reaction of 6-aminohexanonitrile or 6-aminohexamidine amine to ε-caprolactam, suitably at Ammonia is separated before extraction, for example by distillation or steam stripping. In distillation, any unconverted 6-aminocapronitrile (in method (I)) and part of the water are usually separated together. After this ammonia gas separation, the concentration of ε-caprolactam in the resulting aqueous mixture containing 6-aminohexanoic acid and 6-aminohexamidineamine and oligomers if necessary, will preferably be greater than The reaction of 10% by weight εε-caprolactam can be carried out continuously, and the aqueous mixture obtained in the extraction according to the present invention is preferably recovered to the cyclization process as described in (I), (II) and (III) above, It has been found that compounds such as 6-aminohexanoic acid, 6-aminohexamidine and oligomers present in the mixture can be reacted to ε-caprolactam in a high yield, so ε- Caprolactam can also be used to obtain a useful recovery gas stream and can be successfully used to produce more ε-caprolactam. The aqueous mixture is recycled to the reaction zone prior to cyclization, separating any alcohol solvent than in the aqueous phase will be advised, this separation more appropriate to carry out distillation, steam distillation and more is appropriate. In a preferred embodiment for the preparation of ε-caprolactam, the following steps are performed:

This standard is applicable to Chinese national standard (€ milk) 8 4 specifications (210, / 297 mm) TgT (Please read the precautions on the back before filling this page), order 496862 A7 B7_ V. Description of the invention (6) (i) An aqueous mixture containing 6-aminohexanoic acid, 6-aminohexamidine and its individual oligomers is reacted in a liquid phase in a reactor at 270 to 350 ° C to form ε-caprolactam. amine. (ii) Separating ammonia gas from the obtained aqueous mixture to a concentration of less than 0.1% by weight. (iii) Extraction of ε-caprolactam from the aqueous mixture obtained in step (Π) via the method according to the present invention. , Resulting in the formation of residual liquid phase and alcohol extraction liquid phase. (iv) contacting the aqueous residual liquid phase with the vapor to remove any dissolved alcohol solvent from the residual liquid phase. (v) recovering the aqueous phase obtained in step (iv) to step (i). (vi) ε-caprolactam is separated from the alcohol phase, and the resulting alcohol solvent is repeatedly used in step (iii). The temperature in step ⑴ is preferably 270 to 350 ° C, and more preferably higher than 290 ° C. The pressure in step ⑴ is preferably 5.0 to 20 MPa. Generally, the pressure will be greater than or equal to the pressure obtained by the liquid reaction mixture and the use temperature. . Printed by the Consumers' Cooperative of the Central Standards Bureau of the Ministry of Economic Affairs (please read the precautions on the back before filling out this page). An example of a possible process diagram for the above specific embodiment is described in FIG. 1. The starting materials are fed to the cyclization reactor (A), and the ammonia (c) is separated from the aqueous reactor effluent (b) in the distillation (B), and ε-caprolactam, 6-amine Aqueous liquid mixture (d) of hexanoic acid, 6-aminohexamidine and its individual oligomers is fed to an extraction column (C), and countercurrent water (g) is supplied in this column and at the same time Alcohol solvent (h) is also supplied, and the obtained alcohol extraction phase (e) is fed to the distillation column (D), where the lower boiling alcohol and dissolved water are separated via ⑴ and ε-caprolactam product ⑴, in The liquid / liquid separator (E) separates alcohol from water, resulting in countercurrent water (g) (depending on the paper size, the Chinese National Standard (CNS) A4 specification (210X297 mm) 7010 496862 A7 B7 V. Description of the invention (7) Need to contain the same alcohol) and alcohol solvent stream (h) (containing partially dissolved water as needed), and feed the aqueous residual liquid phase To the steam stripper (F) any alcohol present in rhenium and any excess water are separated via rhenium to separate 6-aminohexanoic acid, 6-aminohexamidine and its individual oligomers and as needed The small amount of ε-caprolactam obtained in the obtained aqueous mixture (k) was recovered to the reactor (A). The invention will now be illustrated by the following non-limiting examples. The partition coefficient is defined as the quotient of the concentration (wt%) of a substance in the alcohol extraction phase and the concentration (wt%) in the aqueous residual liquid phase.

Example I An oligomer containing 15.5% by weight of ε-caprolactam, 5.2% by weight of 6-aminohexanoic acid, 17.4% by weight of 6-aminohexamidine and 2.2% by weight of 6-aminohexanoic acid, and 3.4 100 g of an aqueous mixture of an oligomer of 6-aminohexamidine is thoroughly mixed with 100 g of 4-monomethyl-2-pentanol at 80 ° C, and equilibrium is reached for a sufficient time. Printed by the Consumers' Cooperative of the Central Standards Bureau of the Ministry of Economic Affairs, the distribution coefficient of ε-caprolactam is 3.3. No oligomers of 6-aminocaproic acid and 6-aminocaproic acid were detected in the alcohol phase. The partition coefficient of aminohexamidine is 0.45 and the partition coefficient of 6-aminohexamidine oligomer is 0.66.

Example II: Put a 3m glass Reinforced circle (6mm) into a pulsating filled extraction column (2.5cm in diameter) placed vertically, feed the aqueous product 1m below the top, and countercurrently at 60 ° C. Water is supplied to the top and 4 -methyl ^ is supplied from the bottom. The paper size is in accordance with Chinese National Standard (CNS) A4 (210X297 mm) _ 1〇 '~ 496862 A7 B7 V. Description of the invention (8) 2-pentanol, supply The rate is 1.6 5 kg / hr of countercurrent water for water product feed. 0.3 1 kg / hr of 4 monomethyl-2-pentanol 1.10 kg / hr. The composition is: 18.1% by weight of the aqueous product. Caprolactam 1.28% by weight. 6-Aminohexanoic acid (6ACA) 0.73% by weight 6-Aminohexanamine (6ACAM) 2.89% by weight of 6ACA and 6ACAM oligomers. On the top of the alcohol phase (approximately 15% by weight of water), the content obtained was 19.1% by weight of caprolactam (99.6% yield) < 0.01% by weight of 6-aminohexanoic acid < 0.01% by weight of 6-aminohexanone Amine < 0.01% by weight of oligomers The Consumer Cooperatives of the Central Standards Bureau of the Ministry of Economic Affairs printed less than 1% of 6-aminohexamidine, 6-amino S acid and oligomers that had been lost to the alcohol phase. Ε-caprolactam, which is still present in the resulting aqueous phase, cannot be considered a loss when this mixture is reused in the process and 6ACA, 6ACAM and oligomers are converted to ε-caprolactam. This paper size applies to China National Standard (CNS) A4 specification (210X297 mm) -11-

Claims (1)

496862 VI. Annex I (a) of the scope of patent application: \ Patent application No. 86 1 0 1 201 A01 Amendment of Chinese patent scope Amendment of the Republic of China in February 1990 1. A 6-aminohexamidine and 6- A method for the phase separation of aminohexamidine oligomers from epsilon-caprolactam, in which epsilon-caprolactam, 6-aminohexamidine and 6-aminohexamidine oligomers exist in the In an aqueous starting mixture, this mixture is contacted with a mono-alcohol extraction solvent containing 4 to 12 carbon atoms at a temperature between room temperature and 200 ° C to produce the first containing a small amount of ε-caprolactam Aqueous residual liquid phase and ε-caprolactam-rich alcohol phase, and 6-aminohexamidine and / or 6-aminohexamidine oligomers in the alcohol phase, the latter alcohol phase followed Contact with water (counter-current water) at room temperature and a temperature between 200 ° C to produce alcohol-extracted phase friends containing a small amount of 6-aminohexamidine and / or 6-aminohexamidine oligomers A second aqueous residual liquid phase of 6-aminohexamidine amine and / or 6-aminohexamidine oligomer. 2. The method of claim 1 in which the alcohol extraction solvent is a monoalcohol containing 5-8 carbon atoms. 3. The method of claim 2 in which the monoalcohol is a hindered alcohol. 4. The method of claim 3, wherein the alcohol is 4-methyl-2-pentanol. 5. The method according to any one of claims 1 to 4, wherein 6-aminohexanoic acid and / or 6-aminohexanoic acid oligomers are also present in the first aqueous starting mixture. ----------------- 丨 丨 tri -------- Qi, (Please read the precautions on the back before filling out this page) Staff Consumption of Intellectual Property Bureau, Ministry of Economic Affairs Printed by the cooperative -n I nnnn · ϋ nnn I n ϋ lt < This paper size applies to China National Standard (CNS) A4 (210 X 297 mm) -1-496862 A8 B8 C8 D8 VI. Patent Application Scope (please (Please read the notes on the back before filling this page) 6. If you apply § 靑, the method of any one of the patent scope 丨 to 4, the method in which the first aqueous starting mixture contains 0.5 to 10% by weight of oligosaccharides Polymer, ε-caprolactam between 5-30% by weight, 6-aminohexanoic acid between 0.1-10% by weight, and 6-aminohexanylamine between 0.1-10% by weight. 7. The method according to any one of claims 1 to 4 in § 靑, where the temperature is between 50 ° and 130 ° C. '8. The method according to any one of claims 1-4, wherein the extraction is performed continuously and wherein the first aqueous residual liquid is mixed with the first aqueous starting mixture. 9. The method according to item 8 of the patent application, wherein the method is performed in a container placed vertically, wherein the aqueous starting mixture is fed in the middle of the container, the alcohol extraction solvent is fed to the bottom of the container, and the water is countercurrent. Feed to the top of the container, and the obtained aqueous residual liquid and alcohol extraction phase are obtained at the bottom and top of the container, respectively. 1 0. A method for preparing ε-caprolactam, wherein the following steps are performed: (i) an aqueous mixture containing 6-aminocaproic acid, 6-aminocaproamide and individual oligomers thereof is dissolved in a liquid In contrast, ε-caprolactam is reacted in a reaction zone at a temperature between 270 and 350 t, printed by the Intellectual Property Office of the Ministry of Economic Affairs and Consumer Cooperatives. (Ii) Ammonia is separated from the resulting aqueous mixture to a concentration Less than 0.1% by weight, (lii) extracting ε-caprolactam from the aqueous mixture obtained in step (U) via the method according to any one of claims 1 to 9 of the patent application scope to produce an aqueous residual liquid phase and an alcohol Extract the liquid phase, (iv) contact the aqueous residual liquid phase with the vapor, and apply any dissolved alcohol solvent from the residual liquid to the paper standard of China National Standard (CNS) A4 (210 X 297 mm) -2-496862 A8 B8 C8 D8 Phase separation in the scope of patent application, > (V) recovering the aqueous phase obtained in step (IV) to step U), (Vi) separating ε-caprolactam from the alcohol phase, and The alcohol solvent is repeatedly used in step (111). -----------_ 象 -------- ITir ------% # (Please read the precautions on the back before filling out this page) Staff Consumption of Intellectual Property Bureau, Ministry of Economic Affairs The paper size printed by the cooperative is applicable to the Chinese National Standard (CNS) A4 (210 X 297 mm) -3-