GB978746A - Process for the recovery of phenols from impure aqueous solutions - Google Patents

Abstract

978,746. Purifying phenols. K.-F. STILL, [trading as FIRMA CARL STILL]. July 6, 1961 [July 21, 1960], No. 24555/61. Heading C2C. Phenols are recovered from impure neutral or ammoniacal phenol-containing aqueous solutions or alkaline aqueous solutions supersated with phenols by solvent extraction with a branched chain aliphatic alcohol containing up to 20 carbon atoms or a mixture of such alcohol with an ester ether and/or hydrocarbon containing at least 20% by weight of the alcohol in a proportion amounting to 30 to 200% by weight of the aqueous phenol-containing solution, such alcohol or mixture boiling above 230‹C. and being a primary and/or secondary product of oxo-synthesis followed by hydrogenation, and the phenols separated from the solvents by distillation. The extraction may be effected, for example, by countercurrent treatment in extraction columns and at temperatures of over 30‹C., preferably over 40‹C. The solvent may be a primary product of oxo-synthesis which has been subjected to an aldol condensation and prior to the hydrogenation. Secondary products of oxosynthesis which contain unstable compounds (acetals and esters), before being used as the solvent, may be subjected to distillation under atmospheric or superatmospheric pressure with a dilute acid to split up the unstable compounds, the products of splitting being distilled off and the distillate hydrogenated to yield utilizable alcohols. This pretreatment may be omitted if, after the solvent extraction, the phenols are separated from the solvent by distillation in the presence of a small quantity of water and sufficient alkali such that the splitting of the unstable compounds does not occur. Small amounts of solvent present in the dephenolised aqueous solution may be removed by filtration through an absorbent material, e.g., granular coke, pumice stone, silica gel or clay, and recovered therefrom by treatment with steam or a solvent. The solvent residue may also be removed by centrifugation or by washing with a hydrocarbon fraction e.g. an aromatic fraction boiling between 100‹C. and 200‹C. The aqueous starting solution is advantageously subjected to a preliminary washing with an aliphatic or aromatic hydrocarbon boiling below 160‹C., the washing agent being re-used for further preliminary washing after the impurities taken up, e.g. naphthalene, have been removed therefrom e.g. by distillation. The phenol containing extraction agent is distilled, preferably under reduced pressure, to separate the phenols therefrom. Tarry impurities are removed from the remaining solvent, preferably by settling for 3 to 10 hours, and the solvent thereafter purified by washing with a dilute aqueous solution of an alkali and/or distillation and re-used into the extraction process. The phenol rich product obtained may be fractionated and the product split up into carbolic acid, orthocresol, meta- and para cresol and xylenol fractions