Process for purifying crude 4-aminophenol
US4870209A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 29, 1987 |
| Grant date | Sep 26, 1989 |
| Priority date | — |
| Expiry date | Apr 29, 2007 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC07C215/76
- WIPO fieldOrganic fine chemistry
- WIPO sectorChemistry
Abstract
A process for the purification of crude 4-aminophenol which was prepared by the catalytic hydrogenation of nitrobenzene in aqueous sulfuric acid is described involving: adjusting the pH of an aqueous solution of crude 4-aminophenol to pH 4.0-5.0 at a temperature between 75.degree. C. and 85.degree. C.; mixing the aforesaid solution with toluene as the solvent, in order to extract various impurities and the dissolved nitrobenzene starting material; adjusting the pH of the resultant solution as required to maintain it at pH 4.0-5.0; allowing the resultant mixture to settle thereby forming a top organic layer and a bottom aqueous raffinate layer which raffinate contains 4-aminophenol and the by-product material, ortho-aminophenol; separating the two layers and repeatedly extracting the raffinate layer which toluene at pH 4.0-5.0 at a temperature of 75.degree.-85.degree. C. until most impurities have been removed from the resultant final raffinate; adding to the resultant raffinate, a charcoal decolorizing agent and a sodium sulfite type salt, which are then removed, leaving a filtrate which contains the 4-aminophenol and also the by-product ortho-aminophenol; adjusting the pH of said …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.