CA1309404C - Process for purifying caprolactam - Google Patents
Process for purifying caprolactamInfo
- Publication number
- CA1309404C CA1309404C CA000573088A CA573088A CA1309404C CA 1309404 C CA1309404 C CA 1309404C CA 000573088 A CA000573088 A CA 000573088A CA 573088 A CA573088 A CA 573088A CA 1309404 C CA1309404 C CA 1309404C
- Authority
- CA
- Canada
- Prior art keywords
- process according
- caprolactam
- active agent
- comprised
- toluene
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07D—HETEROCYCLIC COMPOUNDS
- C07D201/00—Preparation, separation, purification or stabilisation of unsubstituted lactams
- C07D201/16—Separation or purification
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Other In-Based Heterocyclic Compounds (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
- Nitrogen And Oxygen Or Sulfur-Condensed Heterocyclic Ring Systems (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE:
The present invention relates to a process for purifying caprolactam (CL) obtained by Beckmann transposition or by nitrosation of cyclohexylic compounds, characterized in that it is performed in the following steps: (a) the caprolactam oil is treated with ammonia up to a pH comprised between 8 and 10 and at least one surface-active agent is added; (b) the caprolactam in aqueous-ammoniacal solution obtained in (a) is extracted with toluene; (c) the caprolactam in toluene solution according to (b) is extracted with water; (d) the product extracted in (c) is dehydrated by water distillation and is rectified in vacuum, in packed columns, with separation of the low-boiling and high-boiling byproducts in two successive phases; (e) the caprolactam obtained in (d) is treated with (a), an alkaline and/or alkaline-earth hydroxide, until an a/CL weight ratio comprised between 0.0125 and 0.100 equivalents of (a) per kg of CL is obtained, and is subsequently kept under mixing in an inert-gas atmosphere mixing for at least 150' at a temperature comprised between 80° and 160°C; (f) the mixture obtained in (e) is rectified in vacuum, obtaining pure caprolactam.
The present invention relates to a process for purifying caprolactam (CL) obtained by Beckmann transposition or by nitrosation of cyclohexylic compounds, characterized in that it is performed in the following steps: (a) the caprolactam oil is treated with ammonia up to a pH comprised between 8 and 10 and at least one surface-active agent is added; (b) the caprolactam in aqueous-ammoniacal solution obtained in (a) is extracted with toluene; (c) the caprolactam in toluene solution according to (b) is extracted with water; (d) the product extracted in (c) is dehydrated by water distillation and is rectified in vacuum, in packed columns, with separation of the low-boiling and high-boiling byproducts in two successive phases; (e) the caprolactam obtained in (d) is treated with (a), an alkaline and/or alkaline-earth hydroxide, until an a/CL weight ratio comprised between 0.0125 and 0.100 equivalents of (a) per kg of CL is obtained, and is subsequently kept under mixing in an inert-gas atmosphere mixing for at least 150' at a temperature comprised between 80° and 160°C; (f) the mixture obtained in (e) is rectified in vacuum, obtaining pure caprolactam.
Description
~309404 PROCESS FOR PURIFYING CAPROLACTAM
The present invention relates to an ecologically improved process for the purification of caprolactam.
In literature methods are known for purifying caprolactam starting from:
a) its solutions in H2SO4 after Beckmann transposition of cyclohexanonoxime, or b) solutions in H2SO4 of the product obtained by nitrosation of cyclohexylic compounds and extraction of the unreacted cyclohexylic compound.
Said known methods are characterized by the following steps:
1) neutralization of the sulphuric acid with NH3 thus obtaining of the so-called "lactam oil" which stratifies on the saturated solution of ammonium sulphate;
The present invention relates to an ecologically improved process for the purification of caprolactam.
In literature methods are known for purifying caprolactam starting from:
a) its solutions in H2SO4 after Beckmann transposition of cyclohexanonoxime, or b) solutions in H2SO4 of the product obtained by nitrosation of cyclohexylic compounds and extraction of the unreacted cyclohexylic compound.
Said known methods are characterized by the following steps:
1) neutralization of the sulphuric acid with NH3 thus obtaining of the so-called "lactam oil" which stratifies on the saturated solution of ammonium sulphate;
2) caustification of the lactam oil with NaOH (to salify the acid impurities);
3) extraction with toluene (or with another equivalent solvent) of the caprolactam from the caustic oil;
4) various appropriate treatments, such as chemical treatments, re-extraction with water of the caprolactam from the toluene solutions, further chemical treatments and finally evaporations and/or rectifications.
Step (2), i.e. "caustification with NaOH", has two main types of disadvantages:
a) the disposal of the refined product of the extraction of the caprolactam with toluene; this aqueous-alkaline stream contains:
- sodium salts of carboxylic acids - sodium salts of sulphocarboxylic acids.
The only possible disposal system would be the combustion of the entire stream; such combustion, however, is not free from severe disadvantages, since the alkali and the chlorides contained therein corrode and attack the metallic walls and the refractory components of the ovens;
furthermore fusible salts form during the combustion, which on one hand tend to obstruct the ovens, imposing frequent stops, while on the other they create further problems for their disposal, as they are contained in large amounts (of the order of thousands of tonnes/year for an 8000 tonnestyear caprolactam plant);
b) the poor solubility of sodium salts of sulphocarboxylic acids in caustified lactam oil, so that precipitations of said salts occur in the toluene extraction columns, with frequent jamming, entrainment, poor separation of the phases and therefore more or less long stops of the plant.
A caprolactam purification process is also known (U.S. patent 4,606,858) wherein the caprolactam oil is alkalized with ammonia up to a pH comprised between 8 and lo; the caprolactam is then extracted with toluene and purified according to the known art, while the refined product of the toluene extraction is sent to combustion, without the disadvantages due to the presence of sodium.
This process has, however, all the disad~antages related to the chemical treatments required for the purification of caprolactam;
1) high cost of the chemicals;
2) decrease of the purification yield due to reaction of the caprolactam with the chemicals themselves, 3) ecological problems related to the disposal of the waste streams of the treatments.
Another disadvantage of this purification process is the need to recycle considerable amounts of caprolactam, which entails a further decrease of the yield and an increase in management costs.
`
~309~04 The Applicant has now surprisingly found that said disadvantages can be completely eliminated if:
1) a surface-active agent is added to the caprolactam oil when it is alkalized with ammonia to a pH of ~ to lo;
2) the raw caprolactam, after rectification of the low-boiling and high-boiling byproducts and addition of the alkaline and/or alkaline-earth hydroxide, is kept under stirring in an inert-gas atmosphere for at least 150' at a temperature comprised between 80 and 160C.
lo The aim of the present invention is therefore a process for the purification of caprolactam (CL) obtained by Beckmann transposition or by nitrosation of cyclohexylic compounds, characterized in that it is performed in the following steps:
(a) the caprolactam oil is treated with ammonia up to a pH
comprised between 8 and 10, and at least one surface-active agent is added;
(b) the caprolactam in aqueous-ammoniacal solution obtained in (a) is extracted with toluene;
(c) the caprolactam in toluene solution according to (b) is extracted with water;
(d) the product extracted in (c) is dehydrated by water 1~09404 distillation and is rectified in vacuum, in packed columns, with separation of the low-boiling and high-boiling byproducts in two successive phases;
(e) the caprolactam obtained in (d) is treated with (~), an 05 alkaline and/or alkaline-earth hydroxide, until an ~/CL
weight ratio comprised between 0.0125 and 0.100 equivalents of (~) per kg of CL is obtained, and is subsequently kept under mixing in an inert-gas atmosphere for at least 150' at a temperature comprised between 80 and 160C;
(f) the mixture obtained in (e) is rectified in vacuum, obtaining pure caprolactam.
The treatment of the lactam oil with ammonia (step (a)) can be performed with aqueous ammonia or with gaseous ammonia, more preferably up to a pH of approximately 9-9.5.
Such treatment is performed at a temperature comprised between room temperature and 65C, preferably ~or a time period varying between 15 and 120 minutes and more particularly between 45 and 120 minutes.
A non-ionic surface-active agent is preferably used in (a) as surface-active agent, such as for example:
C~l (C~ 0-(CI-I -Cl~2~)6-ll CH3(CH2)8 ~ 0-(CH2-CH20)~-H
C~l (C~ ~ 0-(C~ -Cl~ 0) -~
C113(C~I2)8--- ~ 0-(C~2~ 20)ll C~13(CI~2)8~>_c)-(c~l2-c1l2o)l5 C~13(CII2)14-C-O~C~lz-CHz0)2~
Cl-~3 ( C~ 12 ) 1 o~C~z -- ( Cl l2 2 14 CH3(cH2)l~-cH~-o-(cH2-cH2-o)l~-H
~i CH3(CH2~16-cH2-O-(cH2-cH2-o)l2-H
Tween 20*
Extraction with toluene (according to step (b)) is performed according to known methods at temperatures comprised between 10 and 50OC, preferably between 20 and 40C and more preferably at room temperature.
Both the rectification of the light byproducts and that of the heavy ones may be performed in one or two stages.
The packing of the rectification columns according to steps (d) and (f) is of the high performance and low load loss, "arranged packing" type, as defined in "Perry's Chemical Engineer's Handbook", sixth edition, pages 18-25.
Sodium, potassium or calcium hydroxide is preferably used as alkaline or alkaline-earth hydroxide.
In step ~e), the a/CL ratio is preferably kept between 0.025 and 0.075, the mixing is preferably performed at 80 to 120C for a period comprised between 200 and 300 minutes.
The caprolactam, obtained by the process according to the invention, which is a further object of the present invention, is of the "fiber grade" type.
The following examples are indicative but non-limitative.
Parts are to be considered by weight unless otherwise specified.
Caprolactam is also indicated as CL.
4319 kg/h of CL oil, with 62% CL, obtained by * (trade mark) . ~
. .
: -`:
1309~a04 nitrosation of cyclohexanecarboxylic acid according to the known art, subsequent hydrolysis o~ the mass, neutralization of the sulphuric acid with NH3 and separation of the ammonium sulphate, are alkalized to p~l 9.5 using 59.9 kg/h of NH3 in 28% aqueous solution. Simultaneously with the NH3, 13.97 kg/h of CH3(CH2) B ~ O- (CH2~cH2O)s-H
are also added.
The aqueous solution of raw CL thus obtained is extracted with 26,400 kg/h of toluene in a rotating asymmetric-disk extraction column. The extraction yield is equal to 99.5%. The refined product, constituted by water, byproducts, non-ionic surface-active agent and CL, is sent to combustion.
The CL in toluene solution is re-extracted with 6,160 kg/h of H2O in a column similar to the preceding one.
The extraction yield is 99.6%. The extracted phase is dehydrated by distillation in two successive stages as specified hereafter:
- the first one operates at a pressure of 97 mm of Hg, - the second one at 20 mm of Hg.
The dehydrated CL is sent to the rectification of the low-boiling byproducts, which is performed in two stages.
76 kg/h of a mixture of CL (98.5%) and low-boiling byproducts (1.5%) are obtained from the head of the first column, which has 21 theoretical plates and operates at a pressure of 10 mm of Hg, and are sent to a squeezing column with 19 theoretical plates, operating at a pressure of lo mm Hg; 1.1 kg/h of byproducts and 3.0 kg/h of CL are obtained from the head and are sent to comoustion: 71.9 kg/h of CL
are obtained from the column bottom at 149C and are joined ~..
~,~
1309~04 to the feed of the preceding column.
2.651 kg/h of CL obtained from the bottom of the main column are distilled at 10 mm Hg in a column with 23 theoretical plates, obtaining 2.542 kg/h of distillate and, from the bottom, at 148C, a mixture of 109 kg/h of CL and 26 kg/h of high~boiling byproducts, which is fed to a thin-film evaporator which operates at a pressure of 4 mm Hg and at a bottom temperature of 133C.
The tails, which contain 10 kg/h of CL and 23 kg/h of high-boiling byproducts, are sent to combustion, while the distillate is recycled to the stage of alkalization with NH3.
2,542 kg/h of CL, after rectification of the high-boiling byproducts, are mixed with 5.0 kg/h of NaOH in 48%
aqueous solution and are ketp undar stirring at 120C and in an inert-gas atmosphere for 240', the CL is then distilled at 4 mm Hg in a packed column with a performance equal to 4 theoretical plates, obtaining 2,448 kg/h of pure CL from the head and a mixture of 80 kg/h of CL and of 19 kg/h of sodium salt of ~-aminocapronic acid from the bottom, which is recycled to the hydrolysis phase of the lactamized mass, before the neutralization of the sulphuric acid.
The pure CL obtained has the following characteristics:
Volatile bases Ø1 meq/kg number of KMn04 22,000 seconds The process described in example 1 is followed, except for the following points:
- the CL oil is alkalized to pH 8.5 using 41.8 kg/h of NH3;
- CH3-(CH2)lz-CH2-O-(CH2-CH2-O)14-H is used as non-ionic ., , 1~0940~
surface-active agent;
- the treatment with (a~ is performed with 2.8 kg/h of Ca(OH)2 while keeping the mixture at 100C for 240'.
The CL has the following characteristics:
Volatile bases 0.1 me~/kg number of KMnO4 19,000 seconds The process described in example 1 is followed, except for the following points:
- the CL oil is alkalized to pH 9.0 using 49.7 kg/h of NH3;
- Tween 20 is used as non-ionic surface-active agent;
- the treatment with (a) is performed with 3.6 kg/h of KOH, while keeping the reaction mixture at 90C under stirring for 300'.
The CL obtained has thefollowing characteristics:
Volatile bases 0.1 ~ 0.15 meq/kg number of KMnO4 18,000 seconds The process described in example 1 is followed, except for the following points:
- the CL oil is alkalized to pH 10 using 74 kg/h of NH3;
- CH3(CH2)8 ~ O-(CH2-CH2O)1l-H is used as non-ionic surface-active agent;
- the treatment with (a) is performed using 1.25 kg/h of NaOH while keeping the mixture under stirring at 100C for 300'.
The CL obtained has the following characteristics:
Volatile bases 0.15 + 0.2 meq/kg number of KMnO4 18,000 seconds '1
Step (2), i.e. "caustification with NaOH", has two main types of disadvantages:
a) the disposal of the refined product of the extraction of the caprolactam with toluene; this aqueous-alkaline stream contains:
- sodium salts of carboxylic acids - sodium salts of sulphocarboxylic acids.
The only possible disposal system would be the combustion of the entire stream; such combustion, however, is not free from severe disadvantages, since the alkali and the chlorides contained therein corrode and attack the metallic walls and the refractory components of the ovens;
furthermore fusible salts form during the combustion, which on one hand tend to obstruct the ovens, imposing frequent stops, while on the other they create further problems for their disposal, as they are contained in large amounts (of the order of thousands of tonnes/year for an 8000 tonnestyear caprolactam plant);
b) the poor solubility of sodium salts of sulphocarboxylic acids in caustified lactam oil, so that precipitations of said salts occur in the toluene extraction columns, with frequent jamming, entrainment, poor separation of the phases and therefore more or less long stops of the plant.
A caprolactam purification process is also known (U.S. patent 4,606,858) wherein the caprolactam oil is alkalized with ammonia up to a pH comprised between 8 and lo; the caprolactam is then extracted with toluene and purified according to the known art, while the refined product of the toluene extraction is sent to combustion, without the disadvantages due to the presence of sodium.
This process has, however, all the disad~antages related to the chemical treatments required for the purification of caprolactam;
1) high cost of the chemicals;
2) decrease of the purification yield due to reaction of the caprolactam with the chemicals themselves, 3) ecological problems related to the disposal of the waste streams of the treatments.
Another disadvantage of this purification process is the need to recycle considerable amounts of caprolactam, which entails a further decrease of the yield and an increase in management costs.
`
~309~04 The Applicant has now surprisingly found that said disadvantages can be completely eliminated if:
1) a surface-active agent is added to the caprolactam oil when it is alkalized with ammonia to a pH of ~ to lo;
2) the raw caprolactam, after rectification of the low-boiling and high-boiling byproducts and addition of the alkaline and/or alkaline-earth hydroxide, is kept under stirring in an inert-gas atmosphere for at least 150' at a temperature comprised between 80 and 160C.
lo The aim of the present invention is therefore a process for the purification of caprolactam (CL) obtained by Beckmann transposition or by nitrosation of cyclohexylic compounds, characterized in that it is performed in the following steps:
(a) the caprolactam oil is treated with ammonia up to a pH
comprised between 8 and 10, and at least one surface-active agent is added;
(b) the caprolactam in aqueous-ammoniacal solution obtained in (a) is extracted with toluene;
(c) the caprolactam in toluene solution according to (b) is extracted with water;
(d) the product extracted in (c) is dehydrated by water 1~09404 distillation and is rectified in vacuum, in packed columns, with separation of the low-boiling and high-boiling byproducts in two successive phases;
(e) the caprolactam obtained in (d) is treated with (~), an 05 alkaline and/or alkaline-earth hydroxide, until an ~/CL
weight ratio comprised between 0.0125 and 0.100 equivalents of (~) per kg of CL is obtained, and is subsequently kept under mixing in an inert-gas atmosphere for at least 150' at a temperature comprised between 80 and 160C;
(f) the mixture obtained in (e) is rectified in vacuum, obtaining pure caprolactam.
The treatment of the lactam oil with ammonia (step (a)) can be performed with aqueous ammonia or with gaseous ammonia, more preferably up to a pH of approximately 9-9.5.
Such treatment is performed at a temperature comprised between room temperature and 65C, preferably ~or a time period varying between 15 and 120 minutes and more particularly between 45 and 120 minutes.
A non-ionic surface-active agent is preferably used in (a) as surface-active agent, such as for example:
C~l (C~ 0-(CI-I -Cl~2~)6-ll CH3(CH2)8 ~ 0-(CH2-CH20)~-H
C~l (C~ ~ 0-(C~ -Cl~ 0) -~
C113(C~I2)8--- ~ 0-(C~2~ 20)ll C~13(CI~2)8~>_c)-(c~l2-c1l2o)l5 C~13(CII2)14-C-O~C~lz-CHz0)2~
Cl-~3 ( C~ 12 ) 1 o~C~z -- ( Cl l2 2 14 CH3(cH2)l~-cH~-o-(cH2-cH2-o)l~-H
~i CH3(CH2~16-cH2-O-(cH2-cH2-o)l2-H
Tween 20*
Extraction with toluene (according to step (b)) is performed according to known methods at temperatures comprised between 10 and 50OC, preferably between 20 and 40C and more preferably at room temperature.
Both the rectification of the light byproducts and that of the heavy ones may be performed in one or two stages.
The packing of the rectification columns according to steps (d) and (f) is of the high performance and low load loss, "arranged packing" type, as defined in "Perry's Chemical Engineer's Handbook", sixth edition, pages 18-25.
Sodium, potassium or calcium hydroxide is preferably used as alkaline or alkaline-earth hydroxide.
In step ~e), the a/CL ratio is preferably kept between 0.025 and 0.075, the mixing is preferably performed at 80 to 120C for a period comprised between 200 and 300 minutes.
The caprolactam, obtained by the process according to the invention, which is a further object of the present invention, is of the "fiber grade" type.
The following examples are indicative but non-limitative.
Parts are to be considered by weight unless otherwise specified.
Caprolactam is also indicated as CL.
4319 kg/h of CL oil, with 62% CL, obtained by * (trade mark) . ~
. .
: -`:
1309~a04 nitrosation of cyclohexanecarboxylic acid according to the known art, subsequent hydrolysis o~ the mass, neutralization of the sulphuric acid with NH3 and separation of the ammonium sulphate, are alkalized to p~l 9.5 using 59.9 kg/h of NH3 in 28% aqueous solution. Simultaneously with the NH3, 13.97 kg/h of CH3(CH2) B ~ O- (CH2~cH2O)s-H
are also added.
The aqueous solution of raw CL thus obtained is extracted with 26,400 kg/h of toluene in a rotating asymmetric-disk extraction column. The extraction yield is equal to 99.5%. The refined product, constituted by water, byproducts, non-ionic surface-active agent and CL, is sent to combustion.
The CL in toluene solution is re-extracted with 6,160 kg/h of H2O in a column similar to the preceding one.
The extraction yield is 99.6%. The extracted phase is dehydrated by distillation in two successive stages as specified hereafter:
- the first one operates at a pressure of 97 mm of Hg, - the second one at 20 mm of Hg.
The dehydrated CL is sent to the rectification of the low-boiling byproducts, which is performed in two stages.
76 kg/h of a mixture of CL (98.5%) and low-boiling byproducts (1.5%) are obtained from the head of the first column, which has 21 theoretical plates and operates at a pressure of 10 mm of Hg, and are sent to a squeezing column with 19 theoretical plates, operating at a pressure of lo mm Hg; 1.1 kg/h of byproducts and 3.0 kg/h of CL are obtained from the head and are sent to comoustion: 71.9 kg/h of CL
are obtained from the column bottom at 149C and are joined ~..
~,~
1309~04 to the feed of the preceding column.
2.651 kg/h of CL obtained from the bottom of the main column are distilled at 10 mm Hg in a column with 23 theoretical plates, obtaining 2.542 kg/h of distillate and, from the bottom, at 148C, a mixture of 109 kg/h of CL and 26 kg/h of high~boiling byproducts, which is fed to a thin-film evaporator which operates at a pressure of 4 mm Hg and at a bottom temperature of 133C.
The tails, which contain 10 kg/h of CL and 23 kg/h of high-boiling byproducts, are sent to combustion, while the distillate is recycled to the stage of alkalization with NH3.
2,542 kg/h of CL, after rectification of the high-boiling byproducts, are mixed with 5.0 kg/h of NaOH in 48%
aqueous solution and are ketp undar stirring at 120C and in an inert-gas atmosphere for 240', the CL is then distilled at 4 mm Hg in a packed column with a performance equal to 4 theoretical plates, obtaining 2,448 kg/h of pure CL from the head and a mixture of 80 kg/h of CL and of 19 kg/h of sodium salt of ~-aminocapronic acid from the bottom, which is recycled to the hydrolysis phase of the lactamized mass, before the neutralization of the sulphuric acid.
The pure CL obtained has the following characteristics:
Volatile bases Ø1 meq/kg number of KMn04 22,000 seconds The process described in example 1 is followed, except for the following points:
- the CL oil is alkalized to pH 8.5 using 41.8 kg/h of NH3;
- CH3-(CH2)lz-CH2-O-(CH2-CH2-O)14-H is used as non-ionic ., , 1~0940~
surface-active agent;
- the treatment with (a~ is performed with 2.8 kg/h of Ca(OH)2 while keeping the mixture at 100C for 240'.
The CL has the following characteristics:
Volatile bases 0.1 me~/kg number of KMnO4 19,000 seconds The process described in example 1 is followed, except for the following points:
- the CL oil is alkalized to pH 9.0 using 49.7 kg/h of NH3;
- Tween 20 is used as non-ionic surface-active agent;
- the treatment with (a) is performed with 3.6 kg/h of KOH, while keeping the reaction mixture at 90C under stirring for 300'.
The CL obtained has thefollowing characteristics:
Volatile bases 0.1 ~ 0.15 meq/kg number of KMnO4 18,000 seconds The process described in example 1 is followed, except for the following points:
- the CL oil is alkalized to pH 10 using 74 kg/h of NH3;
- CH3(CH2)8 ~ O-(CH2-CH2O)1l-H is used as non-ionic surface-active agent;
- the treatment with (a) is performed using 1.25 kg/h of NaOH while keeping the mixture under stirring at 100C for 300'.
The CL obtained has the following characteristics:
Volatile bases 0.15 + 0.2 meq/kg number of KMnO4 18,000 seconds '1
Claims (18)
1. Process for purifying caprolactam (CL) obtained by Beckmann transposition or by nitrosation of cyclohexylic compounds, characterized in that it is performed in the following steps:
(a) the caprolactam oil is treated with ammonia up to a pH
comprised between 8 and 10 and at least one surface-active agent is added;
(b) the caprolactam in aqueous-ammoniacal solution obtained in (a) is extracted with toluene;
(c) the caprolactam in toluene solution according to (b) is extracted with water:
(d) the product extracted in (c) is dehydrated by water distillation and is rectified in vacuum, in packed columns, with separation of the low-boiling and high-boiling byproducts in two successive phases:
(e) the caprolactam obtained in (d) is treated with (.alpha.), an alkaline and/or alkaline-earth hydroxide, until an .alpha./CL
weight ratio comprised between 0.0125 and 0.100 equivalents of (.alpha.) per kg of CL is obtained, and is subsequently kept under mixing in inert-gas atmosphere for at least 150' at a temperature comprised between 80° and 160°C:
(f) the mixture obtained in (e) is rectified in vacuum obtaining pure caprolactam.
(a) the caprolactam oil is treated with ammonia up to a pH
comprised between 8 and 10 and at least one surface-active agent is added;
(b) the caprolactam in aqueous-ammoniacal solution obtained in (a) is extracted with toluene;
(c) the caprolactam in toluene solution according to (b) is extracted with water:
(d) the product extracted in (c) is dehydrated by water distillation and is rectified in vacuum, in packed columns, with separation of the low-boiling and high-boiling byproducts in two successive phases:
(e) the caprolactam obtained in (d) is treated with (.alpha.), an alkaline and/or alkaline-earth hydroxide, until an .alpha./CL
weight ratio comprised between 0.0125 and 0.100 equivalents of (.alpha.) per kg of CL is obtained, and is subsequently kept under mixing in inert-gas atmosphere for at least 150' at a temperature comprised between 80° and 160°C:
(f) the mixture obtained in (e) is rectified in vacuum obtaining pure caprolactam.
2. Process according to claim 1, charaaterized in that the treatment according to step (a) is performed up to a pH of 9 to 9.5.
3. Process according to claim 1, characterized in that the treatment of step (a) is performed at a temperature comprised between room temperature and 65 C.
4. Process according to claim 2, characterized in that the treatment of step (a) is performed at a temperature comprised between room temperature and 65 C.
5. Process according to claim 3, characterized in that said treatment is performed for a period of 15 to 120 minutes.
6. Process according to claim 4, characterized in that said treatment is performed for a period of 15 to 120 minutes.
7. Process according to claim 1, 2, 3, 4 or 5 characterized in that at least one non-ionic surface-active agent is used in said step (a).
8. Process according to claim 6, characterized in that at least one non-ionic surface-active agent is used in said step (a).
9. Process according to claim 7, characterized in that at least one surface-active agent chosen from the group consisting of:
CH3(CH2)8O(CH2-CH2O)9-11 CH3(CH2)12-CH2-O-(CH2-CH2-O)14-11 CH3(CH2)8-O-(CH2-CH2-O)11-11 is used as surface-active agent.
CH3(CH2)8O(CH2-CH2O)9-11 CH3(CH2)12-CH2-O-(CH2-CH2-O)14-11 CH3(CH2)8-O-(CH2-CH2-O)11-11 is used as surface-active agent.
10. Process according to claim 8, characterized in that at least one surface-active agent chosen from the group consisting of:
is used as surface-active agent.
is used as surface-active agent.
11. Process according to claim 1, 2, 3, 4, 5, 6 or 8, characterized in that the extraction with toluene, according to step (b), is performed at a temperature comprised between 10° and 50°C.
12. Process according to claim 10, characterized in that the extraction with toluene, according to step (b), is performed at a temperature comprised between 20° and 40°C.
13. Process according to claim 1, 2, 3, 4, 5, 6, 8 or 10, characterized in that the packed of the rectification columns according to steps (d) and (f) is of the high performance and low loss "arranged packing" type.
14. Process according to claim 12, characterized in that the packed of the rectification columns according to steps (d) and (f) is of the high performance and low loss "arranged packing" type.
15. Process according to claim 1, 2, 3 4, 5, 6, 8, 10 or 12, characterized in that sodium hydroxide is used as alkaline hydroxide.
16. Process according to claim 14, characterized in that sodium hydroxide is used as alkaline hydroxide.
17. Process according to claim 1, characterized in that in step (e) the .alpha./CL ratio is kept between 0.025 and 0.075.
18. Process according to claim 17, characterized in that the mixing in inert gas is performed at 80° to 120°C for a period of 200 to 300 minutes.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| IT21548/87A IT1222419B (en) | 1987-07-31 | 1987-07-31 | CAPROLATTAME PURIFICATION PROCESS |
| IT21548A/87 | 1987-07-31 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1309404C true CA1309404C (en) | 1992-10-27 |
Family
ID=11183439
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000573088A Expired - Fee Related CA1309404C (en) | 1987-07-31 | 1988-07-26 | Process for purifying caprolactam |
Country Status (8)
| Country | Link |
|---|---|
| AR (1) | AR244664A1 (en) |
| BR (1) | BR8803787A (en) |
| CA (1) | CA1309404C (en) |
| DE (1) | DE3825524A1 (en) |
| ES (1) | ES2007278A6 (en) |
| IN (1) | IN171456B (en) |
| IT (1) | IT1222419B (en) |
| SU (1) | SU1709905A3 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2781796B1 (en) † | 1998-07-28 | 2000-09-22 | Rhone Poulenc Fibres | LACTAM DEHYDRATION PROCESS |
| ES2429363T3 (en) * | 2001-08-27 | 2013-11-14 | Dsm Ip Assets B.V. | Procedure to distill an alkaline product of caprolactam under reduced pressure |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| IT1173261B (en) * | 1984-02-08 | 1987-06-18 | Snia Bpd Spa | CAPROLATTAME PURIFICATION PROCESS |
-
1987
- 1987-07-31 IT IT21548/87A patent/IT1222419B/en active
-
1988
- 1988-07-08 IN IN480/MAS/88A patent/IN171456B/en unknown
- 1988-07-26 CA CA000573088A patent/CA1309404C/en not_active Expired - Fee Related
- 1988-07-27 DE DE3825524A patent/DE3825524A1/en not_active Withdrawn
- 1988-07-27 AR AR88311523A patent/AR244664A1/en active
- 1988-07-29 SU SU884356218A patent/SU1709905A3/en active
- 1988-07-29 BR BR8803787A patent/BR8803787A/en not_active IP Right Cessation
- 1988-07-29 ES ES8802389A patent/ES2007278A6/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| SU1709905A3 (en) | 1992-01-30 |
| IN171456B (en) | 1992-10-17 |
| ES2007278A6 (en) | 1989-06-01 |
| AR244664A1 (en) | 1993-11-30 |
| DE3825524A1 (en) | 1989-02-09 |
| IT8721548A0 (en) | 1987-07-31 |
| IT1222419B (en) | 1990-09-05 |
| BR8803787A (en) | 1989-02-21 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US8231765B2 (en) | Process for the purification of lactams | |
| CA1263668A (en) | Liquid 2-hydroxy-methylthiobutyric acid and process for the preparation thereof | |
| JP2685181B2 (en) | Acetone recovery method | |
| US3972955A (en) | Process for preparation of isoprene | |
| US5132476A (en) | Process for producing C3 -C4 monoalkylchlorides | |
| NO138023B (en) | PROCESS FOR CLEANING ACRYLIC NITRIL | |
| US2964535A (en) | Purification of nu-methyl pyrrolidone | |
| CA1309404C (en) | Process for purifying caprolactam | |
| CN1596245A (en) | Process for recovering caprolactam | |
| US4119791A (en) | Aqueous recovery of hydroquinone | |
| US4349418A (en) | Production of methylnaphthalenes and tar bases including indole | |
| CA1305187C (en) | Process for preparing bisphenol a | |
| US5151525A (en) | Process for producing 2-oxo-1,3-dibenzyl-4,5-cis-imidazolidinedicarboxylic acid | |
| CN113429316A (en) | Method for refining adiponitrile | |
| US4352941A (en) | Process for purification of phenylhydrazine | |
| US4017482A (en) | Method of purifying caprolactam | |
| US4606858A (en) | Method of purifying caprolactam | |
| US4112244A (en) | Recovery of hydroquinone | |
| US3518071A (en) | Production of nitrophosphate fertilizer and ammonium nitrate-calcium carbonate fertilizers | |
| US2776972A (en) | Recovery of morpholine from aqueous solutions thereof | |
| CA1055419A (en) | Purification of phosphoric acid | |
| US5035775A (en) | Ultrapure hydrazine production | |
| ES2429363T3 (en) | Procedure to distill an alkaline product of caprolactam under reduced pressure | |
| US4089892A (en) | Process for the preparation of percarboxylic acid solutions | |
| SU1544761A1 (en) | Method of extracting sulfur acid catalyst from reaction mass of decomposition of isopropylbenzene hydroperoxide |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed |