GB759010A - Process for the recovery of beta-naphthol from mixtures - Google Patents

Abstract

b -Naphthol is extracted from a hydroperoxide decomposition mixture containing a major proportion of a b -dialkylmethylnaphthalene by contacting the mixture with a single-phase extraction liquid consisting of a liquefied volatile amine of the formula RR11NR1 where R, R1 and R11 are selected from hydrogen, methyl and ethyl (which definition includes ammonia), at a temperature at which the amine is liquid and which is not higher than 40 DEG C., separating the mixture into an amine phase and a hydrocarbon phase, and distilling the amine from the amine phase to recover a residue containing b -naphthol. The hydroperoxide decomposition mixture may be obtained by oxidation of a b -dialkylmethylnaphthalene to the hydroperoxide followed by acid catalysed decomposition to form a mixture of b -naphthol and excess b -dialkylmethylnaphthalene, and separation of all the readily crystallizable b -naphthol to leave a mixture suitable for use in the process of the invention. b -Dialkylmethylnaphthalenes specified are b -isopropylnaphthalene, b -sec-butylnaphthalene and b -cyclohexylnaphthalene. Amines mentioned are ammonia, methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine and the methylethylamines. The quantity of amine used is 10 to 1000 times the weight of b -naphthol present in the mixture. The process may be a batch or continuous countercurrent one and may be carried out if necessary at elevated pressure to maintain the amine in the liquid state and between - 20 DEG C. and + 40 DEG C. at a temperature which will allow separation of the amine phase from the hydrocarbon phase. Since this temperature varies with the b -naphthol content of the amine, the temperature in a continuous process may vary at different stages of the extraction. Alternatively the amine may be allowed to dissolve in the hydrocarbon layer and phase separation is then effected by cooling to the required temperature or by addition of water to an amount not exceeding 25 per cent of the amine weight. Crystallization of the b -dialkymethylnaphthalene in a low-temperature extraction may be prevented by adding hydrocarbons such as hexane, benzene, toluene, or mixed dialkylmethylnaphthalenes. The amine is removed from the amine extract by distillation, any water present is removed by decantation, the b -naphthol is allowed to crystallize from the residue and is separated and further purified while the mother-liquors containing b -dialkylmethylnaphthalene are recycled to the extraction. The amine-extracted b -dialkylmethylnaphthalene may be recycled to the oxidation direct, or after activation by a caustic soda or lime-water wash and/or distillation. In examples: (1) and (2), b -isopropylnaphthalene containing the corresponding hydroperoxide is decomposed with sulphuric acid, the acetone removed, the mixture cooled and crystalline b -naphthol filtered off, the filtrate being countercurrently extracted with an equal amount of liquid ammonia to give b -isopropylnaphthalene free of b -naphthol and an ammonia extract which is evaporated to give a b -isopropylnaphthalene solution from which b -naphthol crystallizes, the mother-liquors and evaporated ammonia being recycled to the extraction; (3), examples (1) and (2) are repeated using mixed mono- and dimethylamine instead of ammonia.