GB681296A - Improvements in or relating to the purification of alcohols - Google Patents

Abstract

Water-immiscible alcohols containing not more than 20 carbon atoms per molecule are purified by distilling the alcohol or mixture of alcohols to remove lower boiling impurities, treating the topped alcohol or alcohols in the liquid phase with an aqueous caustic alkali solution and gas containing free oxygen, separating the alcohol product from the alkali solution and distilling to yield the desired alcohol or alcohols. The feed may be alcohols made in an Oxo synthesis. Octyl and nonyl alcohols are specified. The products may be made into plasticizers of good colour. The final distillation is preferably effected under a vacuum. Air is the preferred gas-containing free oxygen but oxygen and mixtures of oxygen with inert gaseous diluents may be used. Sodium hydroxide solution is preferred, e.g. 10-50 per cent. Thorough mixing without emulsion formation is necessary and emulsion inhibitors may be used. Oxidation inhibitors may also be present. Temperatures generally used are from room to 100 DEG C. At steam bath temperatures the contact time is usually about one to twenty-four hours. An amount of aqueous caustic of from 0.5 to 50 vol. per cent based on the treated alcohol is satisfactory. Air should preferably be 1 to 100 times the theoretical amount required to convert the mercaptans present to disulphide sulphur and is desirably in excess. Atmospheric and, advantageously, reduced pressures may be used. The alcoholic product may be washed before final distillation. In examples, a C8 (iso-octyl) Oxo alcohol is treated as above described with aqueous sodium hydroxide of strengths varying from 0.5-50, vol. per cent NaOH, and temperatures of 25-100 DEG C., whilst contact may be first at an elevated temperature, e.g. for 1-6 hours, and then for a further period at room temperature, e.g. 16-24 hours. Tables are given of various other reaction conditions and the products are evaluated in terms of the colour of their phthalates.