US4440954A
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US
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Process for the purification of p-aminophenol
Assignee: Mallinckrodt Chemical Inc
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Filing: 1981-04-20
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Granted: 1984-04-03
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Expires: 2001-04-20
Abstract
Abstract An improved process for the recovery and extractive purification of p-aminophenol is disclosed. The process involves contacting an aqueous feed solution prepared by catalytic reduction of nitrobenzene in acid medium and containing 4,4-diaminodiphenyl ether, aniline and other minor amine by-products with a base to adjust the pH of the solution to 4.0-5.0, and then extracting the resulting aqueous feed solution with a mixture of aniline and toluene to selectively dissolve 4,4'-diaminodiphenyl ether in the aniline-toluene mixture and to produce an aqueous phase containing principally p-aminophenol and an organic aniline-toluene phase cotaining p-aminophenol, 4,4'-diaminodiphenyl ether and other amine by-products. The ratio of aniline to toluene is within the range between approximately 4 parts by volume aniline to 1 part by volume toluene and approximately 1 part by volume aniline to 4 parts by volume toluene, preferably a ratio of 1:1. After separation of the aqueous phase from the organic phase, the p-aminophenol of improved purity is recovered from the aqueous phase. Further efficiency in the overall yield of p-aminophenol is achieved by back-extracting the organic phase with a basic solution of potassium or sodium hydroxide to produce an aqueous layer containing the basic solution and substantially all of the p-aminophenol formerly contained in the organic phase and then recycling the aqueous layer for use as a portion of the base used to adjust the pH of the original aqueous feed solution to the range of 4.0 to 5.0. Another feature disclosed is the fractional countercurrent extraction of the original aqueous feed solution having a pH of 4.0 to 5.0 with an aniline-toluene mixture and an ammonium sulfate solution, aniline sulfate or sulfuric acid to selectively dissolve 4,4'-di-aminodiphenyl ether in the aniline-toluene mixture and to produce an aqueous phase from which a greater yield of p-aminophenol of improved purity may be obtained.
Inventors
- 👤 William R. Clingan
- 👤 Edward L. Derrenbacker
- 👤 Thomas J. Dunn
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 23:12
CPC Classifications
C; C07; C07C; C07C209/00; C07C209/82; C07C209/84; C07C215/00; C07C215/74; C07C215/76; C07C211/00; C07C211/43; C07C211/44
Claims Analysis
Total Claims: 36
Claim 1
Independent Claim
155 words
A process for the recovery and extractive purification of p-aminophenol prepared by catalytic reduction of nitrobenzene in acid medium whereby 4,4'-diaminodiphenyl ether and aniline are present as impurities, the process comprising neutralizing an aqueous feed solution containing p-aminophenol and said impurities with a base to adjust the pH of said solution to between approximately 4.0 and 5.0, extracting the resulting aqueous feed solution with an organic solvent consisting of mixtures of aniline and toluene within the range between approximately 4 parts by volume aniline to 1 part by volume toluene and approximately 1 part by volume aniline to 4 parts by volume toluene whereby 4,4'-diaminodiphenyl ether is selectively extracted into said organic solvent and an aqueous phase containing principally p-aminophenol and an organic anilinetoluene phase containing p-aminophenol, 4,4'-diaminodiphenyl ether and other minor amine by-products are produced, separating said aqueous phase from said organic phase and thereafter recovering p-aminophenol of improved purity from said aqueous phase.
Claim 2
Dependent Claim
155 words
A process for the recovery and extractive purification of p-aminophenol prepared by catalytic reduction of nitrobenzene in acid medium whereby 4,4'-diaminodiphenyl ether and aniline are present as impurities, the process comprising neutralizing an aqueous feed solution containing p-aminophenol and said impurities with a base to adjust the pH of said solution to between approximately 4.0 and 5.0, extracting the resulting aqueous feed solution with an organic solvent consisting of mixtures of aniline and toluene within the range between approximately 4 parts by volume aniline to 1 part by volume toluene and approximately 1 part by volume aniline to 4 parts by volume toluene whereby 4,4'-diaminodiphenyl ether is selectively extracted into said organic solvent and an aqueous phase containing principally p-aminophenol and an organic anilinetoluene phase containing p-aminophenol, 4,4'-diaminodiphenyl ether and other minor amine by-products are produced, separating said aqueous phase from said organic phase and thereafter recovering p-aminophenol of improved purity from said aqueous phase.
Claim 3
Dependent Claim
42 words
A process as set forth in claim 1 wherein said base is selected from the group consisting of ammonia, an alkali metal hydroxide, an alkali metal salt of p-aminophenol and a mixture of ammonia and a potassium or sodium salt of p-aminophenol.
Claim 4
Dependent Claim
13 words
A process as set forth in claim 2 wherein said base is ammonia.
Claim 5
Dependent Claim
19 words
A process as set forth in claim 1 wherein the pH of said aqueous feed solution is approximately 4.0.
Claim 6
Dependent Claim
25 words
A process as set forth in claim 1 wherein said organic solvent consists of 50% by volume of aniline and 50% by volume of toluene.
Claim 7
Dependent Claim
24 words
A process as set forth in claim 2 wherein said base is a mixture of ammonia and a solution of potassium hydroxide containing p-aminophenol.
Claim 8
Dependent Claim
36 words
A process as set forth in claim 1 wherein p-aminophenol of improved purity is recovered from said aqueous phase by adjusting the pH of the aqueous phase to between approximately 7.0 to 8.0 to precipitate p-aminophenol.
Claim 9
Dependent Claim
27 words
A process as set forth in claim 1 wherein the volume ratio between the organic solvent and the aqueous feed solution ranges between approximately 0.05:1 and 1:1.
Claim 10
Dependent Claim
15 words
A process as set forth in claim 8 wherein said volume ratio is approximately 0.2:1.
Claim 11
Dependent Claim
27 words
A process as set forth in claim 1 wherein the extraction with said organic solvent is carried out in countercurrent fashion utilizing approximately 5 theoretical extraction stages.
Claim 12
Dependent Claim
24 words
A process as set forth in claim 7 wherein said recovered p-aminophenol is further washed with toluene and a sodium bisulfite solution, and dried.
Claim 13
Dependent Claim
18 words
A process as set forth in claim 1 wherein aniline is recovered from said organic phase by distillation.
Claim 14
Dependent Claim
64 words
A process as set forth in claim 1 wherein said organic phase is treated with a base consisting of a solution of potassium or sodium hydroxide to produce an aqueous layer containing said base and substantially all of the p-aminophenol formerly contained in the organic phase and a residual organic phase containing substantially all of the 4,4'-diaminodiphenyl ether formerly contained in the organic phase.
Claim 15
Dependent Claim
31 words
A process as set forth in claim 13 wherein said organic phase is treated with a base consisting of a solution containing approximately 10 to 50% by weight of potassium hydroxide.
Claim 16
Dependent Claim
71 words
A process as set forth in claim 1 wherein said organic phase is treated with an agent selected from the group consisting of an aqueous ammonium sulfate solution, aniline sulfate and sulfuric acid to produce an aqueous layer containing said agent and substantially all of the p-aminophenol formerly contained in the organic phase and a residual organic phase containing substantially all of the 4,4'-diaminodiphenyl ether formerly contained in the organic phase.
Claim 17
Dependent Claim
26 words
A process as set forth in claim 15 wherein said agent is a 15% aqueous ammonium sulfate solution having a pH between approximately 4.8 and 5.0.
Claim 18
Dependent Claim
24 words
A process as set forth in claim 15 wherein said agent is a 1.5% aqueous ammonium sulfate solution having a pH of approximately 4.0.
Claim 19
Dependent Claim
208 words
A process for the recovery and extractive purification of p-aminophenol prepared by catalytic reduction of nitrobenzene in acid medium whereby 4,4'-diaminodiphenyl ether and aniline are present as impurities, the process comprising contacting an aqueous feed solution containing p-aminophenol and said impurities with a base to adjust the pH of said solution to between approximately 4.0 and 5.0, extracting the resulting aqueous feed solution with an organic solvent consisting of mixtures of aniline and toluene within the range between approximately 4 parts by volume aniline to 1 part by volume toluene and approximately 1 part by volume aniline to 4 parts by volume toluene whereby 4,4'-diaminodiphenyl ether is selectively extracted into said organic solvent and an aqueous phase containing principally p-aminophenol and an organic aniline-toluene phase containing p-aminophenol, 4,4'-diaminodiphenyl ether and other minor amine by-products are produced, separating said aqueous phase from said organic phase, recovering p-aminophenol of improved purity from said aqueous phase, and treating said organic phase with a base consisting of a solution of potassium or sodium hydroxide to produce an aqueous layer containing said base and substantially all of the p-aminophenol formerly contained in the organic phase and a residual organic phase containing substantially all of the 4,4'-diaminodiphenyl ether formerly contained in the organic phase.
Claim 20
Dependent Claim
208 words
A process for the recovery and extractive purification of p-aminophenol prepared by catalytic reduction of nitrobenzene in acid medium whereby 4,4'-diaminodiphenyl ether and aniline are present as impurities, the process comprising contacting an aqueous feed solution containing p-aminophenol and said impurities with a base to adjust the pH of said solution to between approximately 4.0 and 5.0, extracting the resulting aqueous feed solution with an organic solvent consisting of mixtures of aniline and toluene within the range between approximately 4 parts by volume aniline to 1 part by volume toluene and approximately 1 part by volume aniline to 4 parts by volume toluene whereby 4,4'-diaminodiphenyl ether is selectively extracted into said organic solvent and an aqueous phase containing principally p-aminophenol and an organic aniline-toluene phase containing p-aminophenol, 4,4'-diaminodiphenyl ether and other minor amine by-products are produced, separating said aqueous phase from said organic phase, recovering p-aminophenol of improved purity from said aqueous phase, and treating said organic phase with a base consisting of a solution of potassium or sodium hydroxide to produce an aqueous layer containing said base and substantially all of the p-aminophenol formerly contained in the organic phase and a residual organic phase containing substantially all of the 4,4'-diaminodiphenyl ether formerly contained in the organic phase.
Claim 21
Dependent Claim
39 words
A process as set forth in claim 18 wherein said aqueous layer is recycled and utilized as a portion of the base employed to adjust the pH of the original aqueous feed solution to between approximately 4.0 and 5.0.
Claim 22
Dependent Claim
29 words
A process as set forth in claim 18 wherein the base for treating said organic phase is a solution containing approximately 10 to 50% by weight of potassium hydroxide.
Claim 23
Dependent Claim
25 words
A process as set forth in claim 18 wherein said organic solvent consists of 50% by volume of aniline and 50% by volume of toluene.
Claim 24
Dependent Claim
33 words
A process as set forth in claim 18 wherein p-aminophenol is recovered by adjusting said aqueous phase from the pH of the aqueous phase to between approximately 7.0 and 8.0 to precipitate p-aminophenol.
Claim 25
Dependent Claim
27 words
A process as set forth in claim 18 wherein the volume ratio between the organic solvent and the aqueous feed solution ranges between approximately 0.05:1 and 1:1.
Claim 26
Dependent Claim
15 words
A process as set forth in claim 23 wherein said volume ratio is approximately 0.2:1.
Claim 27
Dependent Claim
27 words
A process as set forth in claim 18 wherein the extraction with said organic solvent is carried out in countercurrent fashion utilizing approximately 5 theoretical extraction stages.
Claim 28
Dependent Claim
159 words
A process for the recovery and extractive purification of p-aminophenol prepared by catalytic reduction of nitrobenzene in acid medium whereby 4,4'-diaminodiphenyl ether and aniline are present as impurities, the process comprising fractional countercurrent extraction of an aqueous feed solution containing p-aminophenol and said impurities and having a pH between approximately 4.0 and 5.0 with an organic solvent consisting of mixtures of aniline and toluene within the range between approximately 4 parts by volume aniline to 1 part by volume toluene and approximately 1 part by volume aniline to 4 parts by volume toluene and an agent selected from the group consisting of an ammonium sulfate solution, aniline sulfate and sulfuric acid whereby 4,4'-diaminodiphenyl ether is selectively extracted into said organic solvent and an aqueous phase containing principally p-aminophenol and an organic aniline-toluene phase containing p-aminophenol, 4,4'-diaminodiphenyl ether and other minor amine by-products are produced, separating said aqueous phase and thereafter recovering p-aminophenol of improved purity from said aqueous phase.
Claim 29
Dependent Claim
159 words
A process for the recovery and extractive purification of p-aminophenol prepared by catalytic reduction of nitrobenzene in acid medium whereby 4,4'-diaminodiphenyl ether and aniline are present as impurities, the process comprising fractional countercurrent extraction of an aqueous feed solution containing p-aminophenol and said impurities and having a pH between approximately 4.0 and 5.0 with an organic solvent consisting of mixtures of aniline and toluene within the range between approximately 4 parts by volume aniline to 1 part by volume toluene and approximately 1 part by volume aniline to 4 parts by volume toluene and an agent selected from the group consisting of an ammonium sulfate solution, aniline sulfate and sulfuric acid whereby 4,4'-diaminodiphenyl ether is selectively extracted into said organic solvent and an aqueous phase containing principally p-aminophenol and an organic aniline-toluene phase containing p-aminophenol, 4,4'-diaminodiphenyl ether and other minor amine by-products are produced, separating said aqueous phase and thereafter recovering p-aminophenol of improved purity from said aqueous phase.
Claim 30
Dependent Claim
26 words
A process as set forth in claim 26 wherein said agent is a 15% aqueous ammonium sulfate solution having a pH between approximately 4.8 and 5.0.
Claim 31
Dependent Claim
24 words
A process as set forth in claim 26 wherein said agent is a 1.5% aqueous ammonium sulfate solution having a pH of approximately 4.0.
Claim 32
Dependent Claim
25 words
A process as set forth in claim 26 wherein said organic solvent consists of 50% by volume of aniline and 50% by volume of toluene.
Claim 33
Dependent Claim
36 words
A process as set forth in claim 26 wherein p-aminophenol of improved purity is recovered from said aqueous phase by adjusting the pH of the aqueous phase to between approximately 7.0 and 8.0 to precipitate p-aminophenol.
Claim 34
Dependent Claim
27 words
A process as set forth in claim 26 wherein the volume ratio between the organic solvent and the aqueous feed solution ranges between approximately 0.05:1 and 1:1.
Claim 35
Dependent Claim
15 words
A process as set forth in claim 31 wherein said volume ratio is approximately 0.2:1.
Claim 36
Dependent Claim
31 words
A process as set forth in claim 26 wherein the extraction with said organic solvent and ammonium sulfate solution is carried out in countercurrent fashion utilizing approximately 5 theoretical extraction stages.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 3.5 Years (Year 4) | 1987-04-03 | 1987-10-03 | 1988-04-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-04-03 | 1991-10-03 | 1992-04-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-04-03 | 1995-10-03 | 1996-04-03 | $7700.00 | Window Closed / Lapsed |