Patent GB-772327-A (GB)
Title: A process for sweetening hydrocarbon oil distillates
Inventor: DAVIES THOMAS TREVOR
IPC: C10G29/12
Filed: 1955-08-10
Abstract: Hydrocarbon oil distillates containing mercaptans but substantially no hydrogen sulphide are sweetened by a 2-stage treatment each stage involving the successive application and separation of aqueous alkali metal or alkaline earth metal hypochlorite solution and aqueous caustic alkali solution. Between 0.5 and 2 theories of hypochlorite solution based on the mercaptans present in the distillate is used in the first stage and an amount in the second stage such that the combined total used in the 2 stages is between 1.3 and 3 theories. The treated distillate from the second stage may be subjected to one or more further treatments with aqueous alkali metal or alkaline earth metal hypochlorite and/or caustic alkali solution.  The distillate may also be first treated with an aqueous or aqueous alcoholic solution of an alkali, e.g. a 6-20 per cent solution of an alkali or alkaline earth metal hydroxide to remove sulphur compounds e.g. hydrogen sulphide.  O.05N-3N hypochlorite solutions may be used and may contain free alkali, e.g. 0.051 per cent of alkali metal or alkaline earth metal hydroxides, and may also contain sodium chloride.  6-20 per cent alkali solution may be used to contact the hypochlorite-treated oils.  These alkali solutions may contain water-soluble alcohols, and alkali metal aliphatic or aromatic mercaptides, added as such or in solution in a solvent; for example, caustic alkali solutions used for extracting mercaptans from a hydrocarbon oil may be used, or the oil may be contacted with caustic alkali in the presence of a mercaptan-containing hydrocarbon oil from the same or a different source as the oil treated.  The treatments of the oil with hypochlorite and alkali may be effected by co-current or counter current contacting, by using a rotating disc contactor, perforated discs, baffle plates, a propeller mixer or a turbomixer, or by injecting or spraying one liquid into the other. The oil and aqueous phases may be separated in settling tanks and alkali metal hydroxide solution recycled to the preliminary washing stage.  A batch or continuous process may be used.  The oil at any stage of the process may be filtered, washed with water, treated with solid adsorbents such as alumina and charcoal and the sweetened oil may also be distilled or refluxed over lime. Hydrocarbon oil distillates referred to are those with an end boiling point not more than 370 DEG C., may be fuels e.g. straight-run, thermally or catalytically cracked or reformed gasolines, polymerized gasolines, kerosines, naphthas or aviation turbine fuels.  The sweetened oils may be blended with other oils, such as hydrocarbon oils, e.g. straight-run, thermally or catalytically cracked gasolines, aromatic hydrocarbons such as benzene and toluene, or volatile alcohols and ethers. Compounds such as corrosion inhibitors, e.g. 0.001-2 per cent of aliphatic or cycloaliphatic monocarboxylic acids containing at least 12 carbon atoms, dicarboxylic acids having at least 2 C atoms, and morpholine; oxidation inhibitors, e.g. alkyl phenols and aromatic amines; anti-knock agents, gum inhibitors, detergents and scavenging agents may be added to the sweetened oil.