GB879731A - Process for the preparation of a light hydrocarbon oil freed or substantially freed from mercaptans - Google Patents

Abstract

Colourless or substantially colourless light hydrocarbon oils, e.g. kerosene, gasoline or jet fuel, having a phenol content not below 0.01% by weight and a boiling range of 150 DEG -275 DEG C., are freed from mercaptans by treating the oil in the presence of oxygen with an alkali metal hydroxide solution, suitably potassium hydroxide containing as solutizer (a) a formate and/or an acetate, generally the alkali metal salts, and suitably the potassium salts, and (b) a substance which promotes the solvent power for oxygen, for example a mono-, di- or trihydric alcohol such as diethylene glycol or glycerol, a partial ether of a polyhydric alcohol such as methyl or ethyl "Cellosolve" (Registered Trade Mark), or acids containing alcoholic hydroxyl groups such as tartaric, gluconic or hydroxybutyric acids; triethylene glycol is preferred. The solutizer composition generally comprises 10-70%, preferably 40-65%, by weight of the alkali metal hydroxide solution; in general the weight ratio of (b) to (a) in the solutizer composition is 3:1 to 1:3.5, preferably 1:2 to 1:3 where (a) is a formate, and 3:1 to 1:3, preferably 1:2 to 1:2.5 where (a) is an acetate. The alkali metal hydroxide present in the solution is usually present in an amount of 1-20%, preferably 14-17%, by weight, and the hydroxide solution containing the solutizer is generally mixed with the oil in a volume ratio of 0.05:5, preferably 0.1 to 1. The process is normally carried out at 0-70 DEG C., preferably 15-55 DEG C., at atmospheric pressure, and the oxygen may be used as such or in admixture with inert gas, e.g. as air, generally in an excess of 50-200% over the quantity of mercaptan to be oxidized. Alternatively, a peroxide may be used in amounts of 10-40% of the stoichiometric equivalent of the mercaptans to be oxidized, in which case the oxygen need not be present in excess. The process may be conducted continuously or batchwise, by passing the oil and aqueous solution through a centrifugal mixer or by finely spraying either phase into the other to obtain a fine dispersion, air or oxygen being passed into the oil before or during admixture. If any acids, e.g. hydrogen sulphide, are originally present in the oil, these may be removed by pretreatment, for example with sodium hydroxide. When the process is used with oils obtained by cracking, gums may be prevented from forming by the addition of small amounts of antioxidant to the oil. Specifications 712,056, 759,560, 775,015 are referred to.