GB345632A - Improvements in processes for the recovery and purification of lubricating oils frommineral oils - Google Patents

Abstract

Lubricating oil is produced by distilling a mineral oil under reduced pressure and dewaxing the wax-bearing fraction so produced by mixing with a selective solvent, preferably a mixture of acetone and benzol, cooling the resulting solution, and removing the separated solid components, in which the solvent (1) completely dissolves the fraction at 90 DEG F., (2) has no solvent action on the solid components contained therein at -5 DEG F., and (3) after removal of the separated solids and solvent, yields a purified oil whose cold test is the same as the temperature at which the solid components p <PICT:0345632/III/1> <PICT:0345632/III/2> <PICT:0345632/III/3> were removed from the fraction. A crude petroleum oil is distilled under reduced pressure to yield a wax-bearing fraction of B.P. 400-620 DEG F. which is warmed with a mixture of equal parts of benzol and acetone, and the resulting solution is stirred in a grainer and cooled to -5 DEG F. The mixture is then passed through a filter press to remove the separated wax, and the filtrate is distilled to remove the solvent therefrom. The oil so obtained is freed from sulphur-containing bodies by treatment with sulphuric acid and is thereafter washed with alkali and centrifuged. The resulting purified oil may be fractionated. A suitable apparatus for distilling the oil consists of a heating element 5, Fig. 1, disposed within an evaporator 6 above which is mounted a water-cooled condenser 11 having a discharge pipe 13 and an ejector 16 by which pressure within the apparatus is lowered. The heating element, Fig. 2, consists of an outer shell 22 provided with headers 23, 24 into which tubes 25 are expanded. An inner shell 24<1> is mounted on the header 24 and the annular chambers formed with the outer shell 22 are filled with asbestos or similar packing material 22<1>, 27. The vapour of a high boiling liquid such as diphenyl is supplied to the heater 5 through a pipe 31 from a boiler 32, and rises in the annular space between shells 22, 23, which surrounds the tubes 25, and after passing around the said tubes is discharged through a pipe 35 returning to the boiler 32. The boiler 32 is provided with pressure regulating valves whereby the temperature of the vapour is controlled. In operation, oil passes through a cock 55, a pump 20 and a pipe 21 to the heating element 5, where it rises through the heated tubes 25 and is discharged against a spreader 51. The vaporized oil rises through the opening 9 and after condensation passes through the pipe 13 to the receiver 12. The unvaporized oil passes through a pipe 19 to be recirculated. Diphenyl vapour is generated in the boiler 32 by passing the liquid diphenyl through a pump 39 and pipe 37 to a series of tubes 41 mounted between headers 42, 43 in a brickwork stack 44, which is heated by hot gases. The liquid rises through the said tubes and is discharged against a spreader 62 mounted within a chamber 47 having a safety valve 61. The vapour is discharged through a pressure-regulating cock in the tube 31, and the unvaporized liquid passes through a pipe 48 and a pump 39 to be recirculated.