C - Chemistry – Metallurgy – 07 – C
Patent
C - Chemistry, Metallurgy
07
C
260/612.3
C07C 215/76 (2006.01)
Patent
CA 1152108
PROCESS FOR THE PURIFICATION OF p-AMINOPHENOL Abstract of the Disclosure An improved process for the recovery and extrac- tive purification of p-aminophenol is disclosed. The pro- cess 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 aque- ous feed solution with a mixture of aniline and toluene to selectively dissolve 4,4'-diaminodiphenyl ether in the ani- line-toluene mixture and to produce an aqueous phase con- taining principally p-aminophenol and an organic aniline- toluene phase containing 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, pref- erably 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 effic- iency 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 so- lution to the range of 4.0 to 5Ø Another feature dis- closed 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.
379131
Clingan William R.
Derrenbacker Edward L.
Dunn Thomas J.
Mallinckrodt Inc.
Perley-Robertson Hill & Mcdougall Llp
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