US3717680A
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PURIFICATION OF p-AMINOPHENOL
Assignee: Mallinckrodt Chemical Works
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Filing: 1969-10-16
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Granted: 1973-02-20
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Expires: 1989-10-16
Abstract
Abstract A process is provided for obtaining purified p-aminophenol. The process comprises bringing an aromatic amine from the group of aniline, toluidines, xylidines and mixtures thereof into contact with crude p-aminophenol containing impurities and recovering the purified p-aminophenol. In a particularly important aspect the aromatic amine is brought into contact with an aqueous acid reaction medium containing p-aminophenol and impurities; the pH of the medium is adjusted to above 6 and preferably from about 6.5 to 7.5; the medium is cooled and the purified crystalline paminophenol is removed.
Inventors
- 👤 F Baron
- 👤 R Benner
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 09:03
CPC Classifications
C; C07; C07C; C07C215/00; C07C215/74; C07C215/76; C07C233/00; C07C233/01; C07C233/16
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
113 words
A method for purifying crude p-aminophenol prepared by the catalytic hydrogenation of nitrobenzene in aqueous sulfuric acid which consists essentially of admixing an aromatic amine selected from the group consisting of aniline, toluidines, xylidines and mixtures of xylidines with the crude p-aminophenol at a temperature of from room temperature to the reflux temperature of the mixture and a ratio of 0.2 - 10 parts by weight of aromatic amine per part by weight of p-aminophenol, adjusting the pH of the mixture to 6.5 - 7.5, cooling the resultant mixture to 30*C or below and separating the precipitated p-aminophenol froM the cooled mixture by filtration, thus leaving the impurities contained in the aromatic amine.
Claim 2
Independent Claim
113 words
A method for purifying crude p-aminophenol prepared by the catalytic hydrogenation of nitrobenzene in aqueous sulfuric acid which consists essentially of admixing an aromatic amine selected from the group consisting of aniline, toluidines, xylidines and mixtures of xylidines with the crude p-aminophenol at a temperature of from room temperature to the reflux temperature of the mixture and a ratio of 0.2 - 10 parts by weight of aromatic amine per part by weight of p-aminophenol, adjusting the pH of the mixture to 6.5 - 7.5, cooling the resultant mixture to 30*C or below and separating the precipitated p-aminophenol froM the cooled mixture by filtration, thus leaving the impurities contained in the aromatic amine.
Claim 3
Dependent Claim
12 words
A method as in claim 1 wherein the aromatic amine is aniline.
Claim 4
Dependent Claim
18 words
A method as in claim 1 wherein ammonia is employed to raise the pH value of the solution.
Claim 5
Dependent Claim
13 words
A method as in claim 1 wherein the aromatic amine is mixed xylidines.
Claim 6
Independent Claim
118 words
A method for purifying crude p-aminophenol prepared by the catalytic hydrogenation of nitrobenzene in aqueous sulfuric acid which consists essentially of admixing an aromatic amine selected from the group consisting of aniline, toluidines, xylidines and mixtures of xylidines with an aqueous acidic solution of the crude p-aminophenol at a temperature of from room temperature to the reflux temperature of the mixture and a ratio of 0.2 - 10 parts by weight of aromatic amine per part by weight of p-aminophenol, adjusting the pH of the mixture to 6.5 - 7.5, cooling the resultant mixture to 30*C or below and separating the precipitated p-aminophenol from the cooled mixture by filtration, thus leaving the impurities contained in the aromatic amine.
Claim 7
Independent Claim
118 words
A method for purifying crude p-aminophenol prepared by the catalytic hydrogenation of nitrobenzene in aqueous sulfuric acid which consists essentially of admixing an aromatic amine selected from the group consisting of aniline, toluidines, xylidines and mixtures of xylidines with an aqueous acidic solution of the crude p-aminophenol at a temperature of from room temperature to the reflux temperature of the mixture and a ratio of 0.2 - 10 parts by weight of aromatic amine per part by weight of p-aminophenol, adjusting the pH of the mixture to 6.5 - 7.5, cooling the resultant mixture to 30*C or below and separating the precipitated p-aminophenol from the cooled mixture by filtration, thus leaving the impurities contained in the aromatic amine.
Claim 8
Dependent Claim
12 words
A method as in claim 5 wherein the aromatic amine is aniline.
Claim 9
Independent Claim
160 words
A method for purifying crude p-aminophenol prepared by the catalytic hydrogenation of nitrobenzene in aqueous sulfuric acid which consists essentially of admixing an aromatic amine selected from the group consisting of aniline, toluidines, xylidines and mixtures of xylidines with the crude p-aminophenol at a temperature of from room temperature to the reflux temperature of the mixture and a ratio of 0.2 - 10 parts by weight of aromatic amine per part by weight of p-aminophenol, adjusting the pH of the mixture to 6.5 - 7.5, cooling the resultant mixture to 30*C or below, filtering precipitated p-aminophenol from the cooled mixture on a centrifuge, thus leaving the impurities contained in the aromatic amine, washing the precipitated product with further aromatic amine, subjecting the washed product to washing with an inert low boiling solvent which is miscible with the aromatic amine, subjecting the thus-washed product to washing with an aqueous solution of an oxidation stabilizer for the p-aminophenol and drying the p-aminophenol.
Claim 10
Independent Claim
160 words
A method for purifying crude p-aminophenol prepared by the catalytic hydrogenation of nitrobenzene in aqueous sulfuric acid which consists essentially of admixing an aromatic amine selected from the group consisting of aniline, toluidines, xylidines and mixtures of xylidines with the crude p-aminophenol at a temperature of from room temperature to the reflux temperature of the mixture and a ratio of 0.2 - 10 parts by weight of aromatic amine per part by weight of p-aminophenol, adjusting the pH of the mixture to 6.5 - 7.5, cooling the resultant mixture to 30*C or below, filtering precipitated p-aminophenol from the cooled mixture on a centrifuge, thus leaving the impurities contained in the aromatic amine, washing the precipitated product with further aromatic amine, subjecting the washed product to washing with an inert low boiling solvent which is miscible with the aromatic amine, subjecting the thus-washed product to washing with an aqueous solution of an oxidation stabilizer for the p-aminophenol and drying the p-aminophenol.
Claim 11
Dependent Claim
28 words
A method as in claim 7 wherein the aromatic amine is aniline, the low-boiling solvent is toluene and the aqueous solution is an aqueous solution of sodium bisulfite.
Claim 12
Dependent Claim
12 words
The method according to claim 7, wherein the aromatic amine is aniline.
Claim 13
Independent Claim
162 words
A method for purifying crude p-aminophenol prepared by the catalytic hydrogenation of nitrobenzene in aqueous sulfuric acid which consists essentially of admixing an aromatic amine selected from the group consisting of aniline, toluidines, xylidines and mixtures of xylidines with an aqueous acidic solution of the crude p-aminophenol at a temperature of from room temperature to the reflux temperature of the mixture and a ratio of 0.2 - 10 parts by weight of aromatic amine per part by weight of p-aminophenol, adjusting the pH of the mixture to 6.5 - 7.5, cooling the resultant mixture to 30*C or below, filtering precipitated p-aminophenol from the cooled mixture, thus leaving the impurities contained in the aromatic amine, washing the precipitated product with further aromatic amine, subjecting the washed product to washing with an inert low boiling solvent which is miscible with the aromatic amine, subjecting the thus-washed product to washing with an aqueous solution of an oxidation stabilizer for the p-aminophenol and drying the p-aminophenol.
Claim 14
Independent Claim
162 words
A method for purifying crude p-aminophenol prepared by the catalytic hydrogenation of nitrobenzene in aqueous sulfuric acid which consists essentially of admixing an aromatic amine selected from the group consisting of aniline, toluidines, xylidines and mixtures of xylidines with an aqueous acidic solution of the crude p-aminophenol at a temperature of from room temperature to the reflux temperature of the mixture and a ratio of 0.2 - 10 parts by weight of aromatic amine per part by weight of p-aminophenol, adjusting the pH of the mixture to 6.5 - 7.5, cooling the resultant mixture to 30*C or below, filtering precipitated p-aminophenol from the cooled mixture, thus leaving the impurities contained in the aromatic amine, washing the precipitated product with further aromatic amine, subjecting the washed product to washing with an inert low boiling solvent which is miscible with the aromatic amine, subjecting the thus-washed product to washing with an aqueous solution of an oxidation stabilizer for the p-aminophenol and drying the p-aminophenol.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-02-20 | 1976-08-21 | 1977-02-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-02-20 | 1980-08-21 | 1981-02-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-02-20 | 1984-08-21 | 1985-02-20 | $7700.00 | Window Closed / Lapsed |