Process for purifying crude 4-aminophenol

Details Process for purifying crude 4-aminophenol Process for purifying crude 4-aminophenol

1987-04-29

1989-09-26

Hollrah, Glennon H.

Organic compounds -- part of the class 532-570 series

Organic compounds

Amino nitrogen containing

564416, 564437, C07C 8526, C07C 8511

Patent

active

048702099

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 filtrate to pH 6.5-8.0 and cooling it to a temperature below 10.degree. C.; separating the precipitated pure 4-aminophenol from the by-product ortho-aminophenol which remains in the solution.

REFERENCES:
patent: 3694508 (1972-09-01), Baron et al.
patent: 3845129 (1974-10-01), Reid
patent: 4440954 (1984-04-01), Clingan et al.

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