GB675535A - Removal of carbonyl impurities from organic compounds - Google Patents

Abstract

Aldehydic or ketonic impurities are removed from hydrocarbons and their oxygenated derivatives by adding an aldehyde or ketone thereto to bring the molar ratio of aldehyde to ketone present to about 1-9 : 1, condensing in the presence of a basic condensing agent to give an aldehyde-ketone condensation product which is less volatile than the compound to be purified and separating the latter. Alcohols, particularly lower alkanols made by hydrocarbon oxidation or the Synthol process, hydrocarbons, ethers, esters and acetals may be treated. Formaldehyde, benzaldehyde, furfuraldehyde, and acetaldehyde may be added to condense with ketones present, while acetone, methyl ethyl ketone, acetophenone, and benzophenone may be used for aldehydic impurities. The carbonyl compound may be added as a dilute or concentrated solution or as a polymer. The condensing agent may be an alkali or alkaline earth metal carbonate, bicarbonate, oxide or hydroxide or an organo-metallic base. With formaldehyde the pH should be below 14, and below 12 if alkali metal hydroxides are used. With higher aldehydes, a pH above 14 is suitable. The condensing agent is preferably added in small increments to maintain a pH between 9 and 14+. The condensation product obtained by treating with formaldehyde is a syrup from which a crystalline material may be separated of high hydroxyl content. It may be modified by reaction with additional aldehyde or ketone. In examples: (1) anhydrous or hydrated methanol containing methyl ethyl ketone is treated with paraformaldehyde and potassium carbonate or calcium hydroxide at various temperatures from 50 DEG C. upwards; (2) methanol containing methyl ethyl, diethyl and di-isopropyl ketones is treated with formaldehyde and calcium or sodium hydroxide or potassium carbonate; (3) a fraction of the aqueous products of the Synthol process containing ethanol, propanol, butanol and higher alcohols contaminated with ketones and aldehydes is similarly reacted with paraformaldehyde; (4) crude methanol produced by oxidation of hydrocarbon gases is purified by formaldehyde or acetaldehyde or the hydroxyfraction is purified with benzaldehyde, furfuraldehyde or acetaldehyde or the hydroxymethylated product obtained by condensation of carbonyl impurities with formaldehyde. This product may be used for purification in a first stage followed by formaldehyde in a second; (6) n-heptane is purified from ketones by heating with paraformaldehyde in methanol, sodium methylate in methanol being the condensing agent, and butyl acetate is treated with paraformaldehyde and calcium hydroxide.