US4565890A
Expired / Lapsed
US
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Process for the preparation of N-acetyl-P-aminophenol
Assignee: Mallinckrodt Chemical Inc
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Filing: 1983-10-27
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Granted: 1986-01-21
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Expires: 2003-10-27
Abstract
Abstract An improved process for the preparation of N-acetyl-p-aminophenol. p-Aminophenol is acetylated in an aqueous medium to produce a crude aqueous reaction mixture and N-acetyl-p-aminophenol product is recovered by crystallization from an aqueous system comprising the reaction mixture. Crystals are separated from the crude mother liquor which contains residual N-acetyl-p-aminophenol and unreacted acetic acid. According to the improvement, residual N-acetyl-p-aminophenol and acetic acid are recovered from the crude mother liquor by liquid-liquid extraction with a water-immiscible organic solvent to produce an extract containing N-acetyl-p-aminophenol and acetic acid. The extract is distilled to strip off the solvent and acetic acid.
Inventors
- 👤 Sharad S. Sathe
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 16:17
CPC Classifications
C; C07; C07C; C07C233/00; C07C233/01; C07C233/16
Claims Analysis
Total Claims: 29
Claim 1
Independent Claim
103 words
In a process for the preparation of N-acetyl-p-aminophenol which comprises acetylation of p-aminophenol in an aqueous medium to produce a crude aqueous reaction mixture, recovery of the N-acetyl-p-aminophenol product by crystallization from an aqueous system comprising the reaction mixture, and separation of the crystals from the crude mother liquor, said mother liquor containing residual N-acetyl-p-aminophenol and unreacted acetic acid, the improvement comprising recovering residual N-acetyl-p-aminophenol and acetic acid from the crude mother liquor by liquid-liquid extraction with a water immiscible organic solvent, thereby producing an extract containing N-acetyl-p-aminophenol and acetic acid; and distilling said extract to strip off said solvent and acetic acid.
Claim 2
Dependent Claim
103 words
In a process for the preparation of N-acetyl-p-aminophenol which comprises acetylation of p-aminophenol in an aqueous medium to produce a crude aqueous reaction mixture, recovery of the N-acetyl-p-aminophenol product by crystallization from an aqueous system comprising the reaction mixture, and separation of the crystals from the crude mother liquor, said mother liquor containing residual N-acetyl-p-aminophenol and unreacted acetic acid, the improvement comprising recovering residual N-acetyl-p-aminophenol and acetic acid from the crude mother liquor by liquid-liquid extraction with a water immiscible organic solvent, thereby producing an extract containing N-acetyl-p-aminophenol and acetic acid; and distilling said extract to strip off said solvent and acetic acid.
Claim 3
Dependent Claim
61 words
The process as set forth in claim 1, the improvement comprising the further steps of: mixing the residue from said distillation with water to reduce the solubility of N-acetyl-p-aminophenol in the residue; cooling the resultant mixture of distillation residue and water to crystallize N-acetyl-p-aminophenol therefrom and produce a secondary mother liquor; and separating the crystallized N-acetyl-p-aminophenol from the secondary mother liquor.
Claim 4
Dependent Claim
24 words
The process of set forth in claim 2 wherein said solvent is selected from the group consisting of esters, ketones, alcohols and halogenated solvents.
Claim 5
Dependent Claim
23 words
The process as set forth in claim 3 wherein said solvent comprises a lower alkyl ester of a low molecular weight alkanoic acid.
Claim 6
Dependent Claim
26 words
The process as set forth in claim 4 wherein the extraction is carried out at a temperature of between about 0° C. and about 30° C.
Claim 7
Dependent Claim
24 words
The process as set forth in claim 2 wherein N-acetyl-p-aminophenol and acetic acid are recovered from said crude mother liquor by continuous countercurrent extraction.
Claim 8
Dependent Claim
25 words
The process as set forth in claim 6 wherein said extraction is conducted in a fractional liquid-liquid extraction system comprising at least five equilibrium stages.
Claim 9
Dependent Claim
16 words
The process as set forth in claim 7 wherein said system comprises a reciprocating plate column.
Claim 10
Dependent Claim
23 words
The process as set forth in claim 2 wherein an overhead fraction comprising said solvent is recovered in the distillation of said extract.
Claim 11
Dependent Claim
30 words
The process as set forth in claim 9 wherein said solvent is separated from any aqueous phase in said fraction, and the solvent is recycled for use in said extraction.
Claim 12
Dependent Claim
45 words
The process as set forth in claim 2 in which said solvent comprises an ester having a boiling point not higher than 98° C., and an overhead fraction comprising a concentrated solution of acetic acid substantially free of said solvent is recovered in said distillation.
Claim 13
Dependent Claim
28 words
The process as set forth in claim 11 wherein a substantially solvent-free overhead fraction comprising at least about 65% by weight acetic acid is recovered in said distillation.
Claim 14
Dependent Claim
17 words
The process as set forth in claim 12 wherein said acetic acid fraction comprises glacial acetic acid.
Claim 15
Dependent Claim
27 words
The process as set forth in claim 1 wherein the improvement further comprises contacting the residue from said distillation with an adsorbent for removal of impurities therefrom.
Claim 16
Dependent Claim
32 words
The process as set forth in claim 14 wherein the improvement further comprises combining the purified residue with a further portion of said crude reaction mixture for recovery of N-acetyl-p-aminophenol by crystallization.
Claim 17
Dependent Claim
24 words
The process as set forth in claim 14 wherein said solvent is selected from the group consisting of esters, ketones, alcohols and halogenated solvents.
Claim 18
Dependent Claim
23 words
The process as set forth in claim 16 wherein said solvent comprises a lower alkyl ester of a low molecular weight alkanoic acid.
Claim 19
Dependent Claim
26 words
The process as set forth in claim 17 wherein the extraction is carried out at a temperature of between about 0° C. and about 30° C.
Claim 20
Dependent Claim
24 words
The process as set forth in claim 14 wherein N-acetyl-p-aminophenol and acetic acid are recovered from said crude mother liquor by continuous countercurrent extraction.
Claim 21
Dependent Claim
25 words
The process as set forth in claim 19 wherein said extraction is contacted in a fractional liquid-liquid extraction system comprising at least five equilibrium stages.
Claim 22
Dependent Claim
16 words
The process as set forth in claim 20 wherein said system comprises a reciprocating plate column.
Claim 23
Dependent Claim
23 words
The process as set forth in claim 14 wherein an overhead fraction comprising said solvent is recovered in the distillation of said extract.
Claim 24
Dependent Claim
30 words
The process as set forth in claim 22 wherein said solvent is separated from any aqueous phase in said fraction, and the solvent is recycled for use in said extraction.
Claim 25
Dependent Claim
45 words
The process as set forth in claim 14 wherein said solvent comprises an ester having a boiling point not higher than about 98° C., and an overhead fraction comprising a concentrated solution of acetic acid substantially free of said solvent is recovered in said distillation.
Claim 26
Dependent Claim
28 words
The process as set forth in claim 24 wherein a substantially solvent-free overhead fraction comprising at least about 65% by weight acetic acid is recovered in said distillation.
Claim 27
Dependent Claim
17 words
The process as set forth in claim 25 wherein said acetic acid fraction comprises glacial acetic acid.
Claim 28
Dependent Claim
91 words
In a process for the preparation of N-acetyl-p-aminophenol which comprises acetylation of p-aminophenol in an aqueous medium to produce a crude aqueous reaction mixture, recovery of the N-acetyl-p-aminophenol product by crystallization from an aqueous system comprising the reaction mixture, and separation of the crystals from the crude mother liquor, said mother liquor containing residual N-acetyl-p-aminophenol and unreacted acetic acid, the improvement comprising recovering residual N-acetyl-p-aminophenol and acetic acid from the crude mother liquid by liquid/liquid extraction with a water immiscible organic solvent, thereby producing an extract containing N-acetyl-p-aminophenol and acetic acid.
Claim 29
Dependent Claim
91 words
In a process for the preparation of N-acetyl-p-aminophenol which comprises acetylation of p-aminophenol in an aqueous medium to produce a crude aqueous reaction mixture, recovery of the N-acetyl-p-aminophenol product by crystallization from an aqueous system comprising the reaction mixture, and separation of the crystals from the crude mother liquor, said mother liquor containing residual N-acetyl-p-aminophenol and unreacted acetic acid, the improvement comprising recovering residual N-acetyl-p-aminophenol and acetic acid from the crude mother liquid by liquid/liquid extraction with a water immiscible organic solvent, thereby producing an extract containing N-acetyl-p-aminophenol and acetic acid.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1989-01-20 | 1989-07-22 | 1990-01-21 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-01-20 | 1993-07-22 | 1994-01-21 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-01-20 | 1997-07-22 | 1998-01-21 | $7700.00 | Window Closed / Lapsed |