Patent GB-655690-A (GB)
Title: Improvements in or relating to processes for treating a mixture of hydrocarbons and oxygenated compounds
IPC: C10G21/16
Filed: 1948-08-11
Abstract: Preferentially oil-soluble oxygenated compounds of the group alcohols, aldehydes and ketones are separated from predominantly hydrocarbon solutions thereof by extracting with an aqueous solution containing a substantially non-surface-active salt of a preferentially oil-soluble carboxylic acid, and stratifying and separating an aqueous extract containing said oxygenated compounds. Salts of carboxylic acids of less than 12 carbon atoms as solutions containing about 30-60 per cent by weight are preferred.  Products of the oxidation of hydrocarbon gases or the hydrogenation of oxides of carbon may be so treated.  Alkali metal salts of mixed acids obtained by hydrogenation of carbon monoxide are suitable for the extraction. Sodium, potassium or other alkali metal, ammonium or substituted ammonium salts, e.g. butyrates, valerates, caproates, undecanoates, crotonates, isocrotonates, adipates, azelates, sebacates and fumarates may be used.  Surface-active salts such as myristates, palmitates, oleates and stearates may be present in minor proportions.  Lower aliphatic alcohols are advantageously present up to about 10 per cent.  Separation may be effected in the following steps: (1) Separation of aldehydes and ketones as by formation of solid derivatives or preferably by treatment with bisulphites, such as an excess of a 3-25 per cent aqueous sodium bisulphite, at about 0-40 DEG  C. and a pH of 2.2-8.  Before regeneration of aldehydes and ketones, impurities such as alcohols may be removed by steam distillation or extraction with a solvent such as a light-hydrocarbon or an ether.  (2) Extraction of the hydrocarbon raffinate with a mild alkali to remove carboxylic acids.  (3) Extraction of the raffinate of (2) with caustic alkali to remove phenols.  (4) Extraction of the raffinate with the aqueous salt solution to remove alcohols and residual carbonyl compounds.  The order of steps (2), (3) and (4) may be varied.  The raffinate from (1) may be extracted with a solution of the salt plus a caustic or mild alkali to remove alcohols, carboxylic acids and all or part of the phenols simultaneously.  The salt solutions are used at extraction temperatures sufficient to maintain them fluid, preferably about 20-50 DEG  C.  Recovery of the oxygenated compounds may be effected by steam distillation, solvent extraction or dilution with water and stratification.  Anti-foam agents such as silicones may be added.  Individual components may be separated by known methods.  In examples: (1) a 5 per cent 1-octanol in heptane solution is extracted with aqueous 10, 15 or 20 per cent sodium caprylate, the heptane phase after separation being subjected to five additional extractions, and the aqueous phase being steam distilled to separate the octanol; (2) the hydrocarbon phase from the hydrogenation of carbon monoxide is treated first with 19 per cent sodium bisulphite solution, then with 7 per cent sodium carbonate to remove acids, the salts formed being used in 10 per cent aqueous solution to extract the hydrocarbon raffinate; (3) a similar hydrogenation product is treated with dilute caustic soda to give salts which are used in various concentrations to extract the hydrocarbon raffinate.  The Specification as open to inspection under Sect. 91 comprises also the use as extractant of solutions of phenol or cresol salts. Other salts specified are acetates, propionates, acrylates, malonates, maleates, cyclopentane and cyclohexane carboxylates, benzoates, and phthalates.  The separation of oxygenated compounds generally, including carboxylic acids and phenols, is covered. This subject-matter does not appear in the Specification as accepted.