GB712056A - Processes for converting mercaptans present in gasoline and kerosine into disulphides - Google Patents

Abstract

Mercaptans in gasoline or kerosine are converted into disulphides by intimately contacting with aqueous alkali hydroxide at not more than 60, preferably 30-40 DEG C., in the presence of oxygen but without the addition of oxidation catalysts or contact-promoting substances, at least the theoretical quantity of oxygen for conversion of the mercaptans being present and the volume of the alkali solution being insufficient to dissolve said theoretical quantity, said intimate contacting being effected by mechanical means and being such that the gasoline or kerosine is negative to the doctor test within one hour. A centrifuge, particularly a turbo-mixer, the fan of which rotates at a peripheral speed of at least 5 preferably 8-15 m./sec. or a colloid, for example a Hurrell mill, may be used. Alternatively, the oil and alkali may be sprayed one into the other at high pressure. The treatment time is generally 10-30 mins. Air or oxygen may be dissolved in the oil before or during contact with the alkali but oil in equilibrium with the atmosphere generally contains sufficient oxygen. The disulphides formed pass into the oil and where oils contain .05 per cent. or more of mercaptan sulphur, the greater part may first be removed by known methods. Caustic soda or potash of 5 N or higher is preferred, and solutilisers promoting the solubility of mercaptans may be dissolved therein, generally equivalent to 1-50 per cent. by weight. These include alkylene diamines and alkanolamines, glycols. amino-glycols, di-amino-alcohols, di-amino, di-hydroxy or aminohydroxy-di-alkyl ethers or thioethers, and alkali metal salts of fatty acids, hydroxy or amino-fatty acids, phenyl acetic acid or hydroxy- or amino-phenyl acetic acids or alkylphenols. Where oils containing unsaturateds are treated, such as cracked or reformed gasoline, an anti-oxidant, for example .0001-.01 by weight of an arylamine or alkylphenol, is added. The alkali after separation from the treated oil, is re-used. Examples describe the treatment of synthetic, reformed, and straight run gasolines using 7 N NaoH and air, xylanol being used as a solutiser in one case.