Patent GB-691688-A (GB)
Title: Improvements in or relating to a process of separating organic oxygenated compounds from hydrocarbon solutions
IPC: C07C29/74
Filed: 1950-02-16
Abstract: Preferentially oil-soluble alcohols, aldehydes and/or ketones are separated from solution in hydrocarbons by contacting the solution with an aqueous extractant solution of a solubilizer consisting essentially of at least one salt of an aliphatic monocarboxylic acid having 4 to 6 C atoms in the molecule, and stratifying and separating an aqueous extract containing the preferentially oil-soluble compounds in a purified form.  The solution to be treated may be obtained by the hydrogenation of carbon monoxide and a large number of compounds are stated to be present in such solutions, representative being acetaldehyde, iso-butyraldehyde, acetone, methyl n-butyl ketene, cyclopentanone, methanol, 2-methyl-1-butanol, n-octanol, acetic acid, palmitic acid, methyl acetate, ethyl butyrate, phenols and acetals and ketals.  Acids may be removed by pretreatment with an alkaline solution or together with the oil-soluble compounds by using an alkaline extractant solution.  For maximum extraction the solution should contain above about 30 per cent of solubilizer salts but for optimum hydrocarbon rejection this concentration should be not less than 5 per cent and a preferred range is about 30-50 per cent.  Temperatures specified are preferably about 20-80 DEG  C., e.g. about 30-60 DEG  C.  The hydrocarbon raffinate may be extracted with an aqueous solution of salts of preferentially oil - soluble carboxylic acids, preferably having less than 12 C atoms in the molecule and of concentration above about 30 per cent, in order to remove residual oxygenated compounds. Alternatively treatment with such an extractant may precede extraction with solutions of the invention.  By working in countercurrent and adding water at a succession of points whilst the extractant solution is passing down it is possible to contact the issuing solution of oxygen compounds with a strong, e.g. 50-60 per cent, extractant solution which will give a maximum extraction of these compounds and the successive dilution of the mixture as it passes down will result in the liberation of hydrocarbons, thus aiding in their separation.  The salts are preferably those of an alkali metal, e.g. sodium or potassium, although salts of organic bases such as diethyl-ammonium or triethanolammonium salts, may be used.  Representative of specified salts are isobutyrates, crotonates, 2-methylbutanoates and hexanoates.  Preferably the salts are obtained from straight-chain acids.  The salts may be used separately or as mixtures wherein the acid constituents have an average molecular weight of 88-116, preferably about 95-105. Emulsion formation and foaming may be prevented by the addition of salts of acids of less than 4 C atoms.  The extractant should not contain any large proportion (e.g. about 10 per cent) of monocarboxylic acids containing more than 6 C atoms per molecule. The salts may be obtained by neutralizing the separate acids or mixtures of salts of the specified acids obtained during the hydrogenation of carbon monoxide, by the oxidation of hydrocarbons or mixed aldehydes or by treatment of mixed alcohols with sodium followed by hydration, may be used.  A fraction of alkanoic acids boiling between about 150 DEG  and 210 DEG  C. contains the preferred acids.  In examples, a mixture of hydrocarbons and oxygenated compounds obtained by the hydrogenation of carbon monoxide is extracted with aqueous solutions of the sodium salts of acids obtained in this hydrogenation in (1) salts of C2-C6 acids; (2) salts of all the acids produced during the hydrogenation and then sodium valerate or acetate; (3) salts of individual C4-C9 acids; (4) salts of a C4 acid fraction; (5) salts of a C5 acid fraction; (6) salts of a C6 acid fraction; (7) salts of individual C4, C6, C8, C9, C10 and C12 acids and of the total acids produced during the hydrogenation; and (8) salts of all the acids produced by the hydrogenation and then of individual C4, C5, C6, C7 and C8 acid fractions and the extractive power of the salts of C4-C6 acids in the removal of alcohols, aldehydes and ketones from hydrocarbons compared with that of the salts of the other acids.  Reference has been directed by the Comptroller to Specification 655,690.