GB441703A - Improvements in or relating to methods of and apparatus for treating petroleum hydrocarbon oils and spirits - Google Patents

Abstract

Petroleum oils and spirits are purified by mild oxidation followed by treatment with a light active metal at a temperature between 250 and 500 DEG C., and separation from the impurities formed by this treatment. The oil may be first treated with a light active metal such as sodium, or by hydrogenation, or with solvents or anhydrous alkali hydroxide or chloride. There may be two or more steps of mild oxidation with one or more metal-treatments between. Mild oxidation is such as does not lead to rupture of single bonds between carbon atoms, and may be effected by heating at 200 DEG C. with dinitrotoluene. Other oxidizing agents specified are air and dinitrobenzene. Light active metals are those having an ionization potential of about 6 volts or under and one unpaired electron under the conditions of treatment, and are not limited to the alkali metals. Metals specified are sodium, potassium, calcium and aluminium. The metals may be used together with compounds; substances specified are aluminium in an electrolyzed mixture of sodium and aluminium chlorides, and a mixture of metallic sodium and potassium hydroxide freshly activated by adding sodium or sodamide or by electrolysis. The method of using the <PICT:0441703/III/1> metals is described in Specifications 408,819 and 420,909. The sludge value of a mildly oxidized oil is decreased during treatment with the metal and then increases; the oxidation is controlled by sampling so that the subsequent treatment with metal yields a product of minimum sludge or gum value. The control may be effected by sampling the treated oil in trial runs. When operating with vapours, the colour of a condensate taken at a sampling point is noted, and the rate of flow through a subsequent metaltreatment zone may be varied accordingly. In an example, small amounts of dinitrotoluene from a tank 1 flow into oil in a still 3, heated by an external coil 8 which induces current in the walls of the still. After digestion for a few hours at 200 DEG C., sodium dispersed in kerosene is admitted from the tank 1 and the oil is distilled at 250--300 DEG C., under reduced pressure. The oil may pass through a number of stills 3 in series for successive oxidation and treatment with metal. The residue from the distillation may be treated with fuller's earth or with acid-treated bentonite, the mixture being passed over a drum heated by mercury vapour to remove a fuel oil or lubricating oil of second grade leaving a solid residue suitable for use in purification or in pre-treatment of the oil. The vapours from the still 3 are treated with a catalyst or adsorbent in the vessel 12 to which fixed gases or other vapours may be introduced at 14. The vapours are further treated in the vessel 17 with fused alkali hydroxide containing free active metal, or sodium in fused alkali chloride, or aluminium in fused aluminium chloride. The reagent is recirculated through an oil-separating tank 21, a cell 24 as described in Specification 408,819, and pump tank 28, to the distributer 18. Oil may be introduced at 23 for separating or concentrating the impurities. By this means the surface of the free active metal in the treating agent is kept fresh and clear at the point of contact with the oil vapours. The contents of the pump tank may be protected by inert gas or vapour admitted at 33. The vessel 17 may be replaced by chambers in series, with the hydroxide in one and fused alkali chloride with sodium in another. Gases or light vapours may be admitted at 34. Treated vapours may be sampled at 36 before passing to a further treating vessel 37<1> in which pure sodium at 300 DEG C. or up to 450 DEG C., is circulated continuously in direct current with the vapours. The sodium is circulated through a separator 41 and pump tank 43 to the distributer 38, and the metal may be circulated from the separator 41 through a cell 47 and thence to the vessel 41 or the tank 43. Oil or inert gas may be admitted to the vessels 41, 43 at 51, 52, and the off-take 42 from the vessel 41 may be adjustable vertically. Treated vapours from the vessel 37<1> pass to condensers 54, 55 and separators 56, 57 connected to pressure control at 61. The pressure may vary from \ba1/4\bein. of mercury (absolute) to about 100 lbs. per sq. in. above atmospheric according to the oil used. The quantity of free metal consumed varies from 1 to 20 per cent of the oil. The process may be used for treating lubricating oil which has been hydrogenated, cracked oil, kerosene, or gasoline; for treating Pennsylvania oil to produce lubricant; to reduce the gums and colour and increase the anti-knock value of gasoline; and to produce good gasoline from high-sulphur distillate. The amount of light active metal required may be reduced by a preliminary treatment of the oil with alkali hydroxide or chloride. The Specification as open to inspection under Sect. 91 comprises also the following: Specified metals include lithium, strontium, and copper. The oxidizing-agent may be a mono-nitro aromatic compound containing an alkyl or other substitution group; when dinitrotoluene is used the metal compound is isolated and the less valuable isomers used for the oxidation. A nitro-amino, or di-amino substance may be recovered from the oxidized oil. The oxidation may be carried out in the presence of the active metal, thus air may be blown through liquid oil containing globules of molten sodium. The active metal may be used as vapour. Oil vapour at 190--250 DEG C. may be brought into contact with metallic sodium at a higher temperature, say 300 DEG C. The process may be applied separately to the two fractions into which crude oil is separated by extraction with sulphur dioxide or nitrobenzene, and the used nitrobenzene may serve as the oxidizing agent. This subject-matter does not appear in the Specification as accepted.