Patent GB-389113-A (GB)
Title: Improvements in the separation or purification of lubricating oils
IPC: C10G21/00
Filed: 1931-08-06
Abstract: Materials consisting substantially of oils boiling above 300 DEG  C. are freed from waxes, resins, asphalts, and other impurities so as to produce lubricating oils by treatment with liquefied hydrocarbons composed wholly or mainly of methane, or/and ethane, or/and propane. The raw material, especially if solid at room temperature, may be treated mixed with a liquid solvent, e.g. heavy benzine or kerosene. The liquefied hydrocarbons are advantageously desulphurized before use; they may contain small amounts of saturated hydrocarbon gases of high molecular weight, or/and unsaturated gases, e.g. ethylene or propylene.  The process may be a countercurrent one, but preferably 1-10 kg. of the liquified hydrocarbon and 1 kg. of material are stirred together at 15-40 DEG  C. and raised pressure, or at low temperature and 1-1,5 atmospheres, and the dissolved lubricating oils and other hydrocarbons rich in hydrogen are separated by decantation, filtering, or centrifuging; the separated solution <PICT:0389113/III/1> may be clarified by bleaching earth or other agent, and is then freed from solvent by releasing the pressure with or without heating.  The separation of the impurities from the solution may be promoted by adding active charcoal, kieselguhr, silica gel, bleaching earths, or like agents, and by using vessels containing baffle plates, Raschig rings, or corrugated sheet iron. The liquid hydrocarbon products may be cracked, destructively-hydrogenated, or treated with condensing agents or bleaching earths or liquid solvents, e.g. alcohols, ketones, ketonic acids, nitrobenzene, phenols, aniline, liquid sulphur dioxide, or liquid ammonia.  The separated asphalt may be cracked or destructively-hydrogenated or used for road-making and other purposes.  Raw materials specified are distillative or cracking residues, high-boiling products of destructive-hydrogenation, and crude or waste lubricating oils and distillates; they may first be destructively-hydrogenated.  The liquefied hydrocarbons may be prepared from natural, cracking, destructive-hydrogenative, or other gas mixtures by fractional condensation, by fractional distillation of the condensed gases, or by fractionally releasing the pressure from the liquids obtained by cooling destructive-hydrogenation vapours and reliquefying the desired fraction.  Preferred liquefied solvents are propane, ethane, mixtures of 70-90 per cent of propane with 30-10 per cent of ethane, and mixtures of 75-85 per cent of ethane or/and propane with normally gaseous saturated hydrocarbons of high molecular weight or/and unsaturated hydrocarbons such as propylene or ethylene.  In examples:--(1) Crude Coastal oil is stirred at room temperature and 20 atmospheres with 3 vol. of a liquid mixture of 15 per cent of ethane with 85 per cent of propane; the extract is siphoned off, and warmed to vaporize the solvent.  (2) Pennsylvanian hot steam cylinder oil is treated at 40 DEG  C. with 8-10 vol. of the same solvent; the precipitated impurities are separated, and fractioned into wax and a mixture of resins and asphalts by further treatment with the solvent; or the impurities are destructively hydrogenated at 400-450 DEG  C. and 200 atmospheres in presence of molybdic acid and zinc oxide. Alternatively, the initial treatment is at room temperature to precipitate only the asphalts and resins, and the cleared solution is then cooled to -30-40 DEG  C. to precipitate the wax.  (3) A pitchy residue obtained by distilling German mineral oil is diluted with 25-30 per cent of kerosene and stirred with liquid propane; the extract is decanted over a bleaching earth, and the propane removed by distillation; the product is hot steam cylinder oil; the impurities constitute asphalt.  (4) A mineral oil distillation residue at 40-50 DEG  C. is atomized in a vessel 3 which is continuously fed from a vessel 4 with 8-12 vol. of a mixture of liquefied propane and ethane, and the whole is continuously discharged to a separating vessel 7.  The asphalts and resins are drawn off continuously through a pipe 9 to a vessel 10 in which the pressure is released and the residual ethane and propane expelled by steam or dry heat.  The vapours pass to a condenser 11 and a separator 12, and then through a pipe 13 to a compresser 21; the asphalts and resins are withdrawn and used for road-making. The solution of oil is cooled by water in a cooler 14 and then by a countercurrent of cold propane in a cooler 15; it is passed at 15-20 DEG  C. to one of the vessels 16 . . 19, and is then further cooled in stages by reducing the pressure and causing partial evaporation of the ethane and propane by connecting the vessels 16 . . 19 in turn with the three stages of the compresser 21 through the pipes 20a, 20b, 20c.  At -40 DEG  C. or lower temperature the vessel 16 is emptied through a valve 22, a pump 23, and a vessel 24 to a preferably inclined separator 25 in which paraffin wax separates. The wax-free solution is passed out through a pipe 27 and forced by a pump 29 through an exchanger 30, and through a steam preheater 31 into a pressure still 32; the vaporized ethane and propane is condensed in a water-cooler 40 and passed by a pipe 41 in part to the storage vessel 4 and in part through the exchanger 30, in which it is cooled to -35-40 DEG  C., and through a de-aerating vessel 43 and a pipe 42 to a vessel 44 in which the wax from the vessel 25 is treated with cold solvent.  The oil is passed by a pipe 42b and a pressure release-valve 42a to a column 33 in which the last traces of propane and ethane are expelled by countercurrent steam; it is then taken through a water cooler 36, and a water-separator 37 to a storage vessel.  The vapours from the column 33 are led through a water-cooler 35, a vessel 38 in which water separates, and a pipe 39 to the compresser 21.  The wax and cold solvent in the vessel 44 are passed to a separator 45 in which the wax is repeatedly washed to remove adhering oil, the washing liquid being forced by a pump 46 and a pipe 47 in part to the vessel 4, and in part to the vessels 16 . . 19 to replace the solvent evaporated therefrom.  The washed wax is led to a vessel 48, a steam preheater 49, and a column 50 in which it is freed from propane and ethane by countercurrent steam and is drawn off by a pipe 52, the vapours are passed through a cooler 53 and a water-separator 54 to the pipe 39.  The ethane and propane vapours from the vessels 16 . . 19, 10, 33, 50, 44 after compression in the compresser 21 are liquefied in a water-cooler 59 and passed to the vessel 4.  Losses of propane and ethane are made up by continuously supplying their vapours to the suction side of the compresser 21. These vapours are freed from butane and any other higher boiling constituents by cooling in an exchanger 55 by the cold vapours from the vessels 16 . . 19, and separating in a vessel 57, the liquefied butane &c. evaporating off through a pipe p  58 and an exchanger 56 in which the initial vapours are cooled, and the ethane and propane passing by pipes 58a, 58b to the compresser.  Examples are also given of the use of liquefied butane followed or not by the use of liquefied propane, sulpuric acid, or phenol.  The prior use of benzine, liquefied pentanes or butanes obtained for example from natural gases is also referred to.