GB721914A - Oxidation of hydrocarbons - Google Patents

Abstract

Oxygen-containing organic compounds are obtained by subjecting an aliphatic hydrocarbon containing less than 6 carbon atoms to reaction with oxygen in an oxidation resistant solvent for the hydrocarbon in presence of an oxidation catalyst and of 2 to 20 per cent by weight based on the weight of the solvent of an alkali metal compound or an alkaline earth metal compound. In a modification a weak acid salt of a strong organic base is used instead of the alkali metal or alkaline earth metal compound. The process leads to the formation of increased amounts of esters and ketones in the oxidation product. Specified oxidation catalysts are the salts of metals such as cobalt, nickel, copper, cerium, iron, mercury, chromium, antimony, manganese, uranium, molybdenum, tungsten, tantalum, columbium, vanadium, zirconium, titanium, lead, tin, gold and silver, and particularly the salts of these metals with organic acids such as acetic, propionic, butyric, isobutyric, valeric, benzoic and naphthenic acids. The alkali metal compound or alkaline earth metal compound may be a compound of sodium, potassium, magnesium, barium, calcium or strontium and it is preferred to use a salt of an organic acid, e.g. of formic, acetic, propionic, butyric or isobutyric acid, although other compounds, e.g. salts of hydrocyanic acid or of boric acid may also be used. Specified weak acid salts of strong organic bases which may be used instead of the alkali metal or alkaline earth metal compound are the weak acid salts of quaternary ammonium hydroxides, e.g. of tetralkyl ammonium hydroxides, such as tetramethyl ammonium acetate. Salts which are known to inhibit oxidation, e.g. phenolic salts and salts of bases such as diphenylamine which inhibit oxidation are not suitable. The oxidation may be carried out at 125-225 DEG C. under a pressure of 200 to 2000 pounds per square inch using oxygen as such or in the form of air or other mixture of oxygen with a diluent gas. Suitable oxidation-resistant solvents are acetic acid (e.g. when oxidizing propane, n-butane, isobutane or pentane), propionic acid, butyric acid, valeric acid, methyl acetate, ethyl acetate, benzene and diphenyl. Mixtures of such liquids may also be employed. The process may be carried out batchwise or in a continuous manner. In the latter case the hydrocarbon and oxidizing gas may be introduced at a controlled rate into a reaction vessel charged with the solvent containing the catalyst mixture, the product vapours being condensed to form an upper hydrocarbon layer and a lower aqueous layer containing the water-soluble oxidation products, the hydrocarbon layer being recycled to the reaction zone if desired after separation of the oxidation products dissolved therein. In an example, liquid n-butane, together with air in the form of finely-divided bubbles, is introduced into glacial acetic acid containing cobalt acetate and sodium acetate in a stainless steel reactor maintained at 815 pounds per square inch pressure and at 160-165 DEG C. The process is effected continuously as above and yields a mixture of acetic acid, ethyl acetate, methyl ethyl ketone and a small amount of alcohols. In a comparative example which is carried out under the same reaction conditions but without employing sodium acetate the product obtained contains more acetic acid and less of the other specified products.