GB441105A - A process for separating lubricating hydrocarbon oils into their components - Google Patents

Abstract

Hydrocarbon oils consisting of or containing lubricating oils are separated into their components by treating with two solvents led in countercurrent one of which consists of one or more saturated hydrocarbons containing at least 3 and not more than 11 carbon atoms, and the other consists of a selective solvent chosen from the group:--liquid sulphur dioxide, phenols, furfurol or its derivatives, chlorex (dichlor ethylether), aromatic or aliphatic nitro compounds, nitriles or aldehydes, organic rhodanides or amines, esters of mono- or poly-valent alcohols, ketones, alcohols, nitro aniline, or nitro anisole, the treatment being controlled so that the selective solvent removes substantially only aromatic compounds or components which are easily sulphonizable, poor in hydrogen, and of high refractive index and viscosity. This separation treatment is effected by controlling the temperature, by addition of diluents such as benzol, toluol, ether or naphthalene, or by increasing the flow of one of the solvents. The boiling range of the saturated hydrocarbon lies outside that of the lubricating oil being treated. Saturated hydrocarbons specified are:--propane, pentane, butane, hexane, nonane, gasoline, petroleum ether, tetra hydronaphthalene or deca hydronaphthalene. Selective solvents specified are: furfuryl alcohol, nitrobenzene, nitromethane, nitronaphthalene, acetonitrile, monochlor-acetonitrile, maleic nitrile, succinic nitrile, naphthonitrile, benzonitrile, methyl rhodanide, aniline, naphthylamine, methyl formate or acetate, glycol formate, benzyl, methyl or ethyl alcohol, glycol, thiophene aldehyde, propion aldehyde, acetaldehyde, benzaldehyde, acetone, methyl ethyl ketone or naphthyl phenyl ketone. The pairs of solvents selected are preferably of different molecular weight to raise the critical solution temperature of the mixture. A lubricating oil distillate which may be obtained by destructive or non-destructive distillation of a crude oil is introduced into the middle of an extraction column through which liquid sulphur dioxide and spindle oil flow in countercurrent. The sulphur dioxide removes aromatic and asphaltic ingredients together with any sulphur coloured compounds, and is drawn off. If saturated compounds are present in the extract the flow of the paraffinic solvent is increased. The extraction may be effected in a series of mixing and settling vessels or by introducing the oil and hydrocarbon solvent separately or mixed together at one end of the extraction column and the selective solvent at the other end. The selective solvent may travel over a part of the column and a temperature gradient over that part may be applied. The refined lubricating oil obtained from the saturated hydrocarbon extract may be submitted to a final treatment with sulphuric acid or with a bleaching earth. The oils are dewaxed if necessary before the extraction treatment. The process may also be applied to regenerating waste lubricating oils.