Improvements in or relating to the refining of mineral oil and the preparation of lubricating oil

摘要

Mineral oils are separated into their paraffinic and naphthenic constituents by treating with a paraffinic and a general naphthenic solvent flowing in countercurrent, the two solvents being immiscible whereby the oil is separated into layers from which the respective constituents are recovered. The paraffinic solvents used consist of petroleum ether or liquefied normally gaseous hydrocarbons such as ethane, propane or butane. General naphthenic solvents used are nitrobenzene, nitrotoluene benzaldehyde, or pyridine; these solvents dissolve all the naphthenic constituents as distinct from limited solvents such as sulphur dioxide, furfural or aniline which dissolve only asphaltic and aromatic substances. The latter solvents may be used in admixture with the general naphthenic solvents in the treatment of asphaltic base oils. Preferably the two counter-flowing solvents used have boiling ranges which do not overlap. A Californian crude oil, or lubricating oil distillate therefrom, is admitted to the centre of an extraction column through which propane and nitrobenzene flow in counter current. Extraction is effected under pressure and at a temperature of about 4 DEG C. at which the solvents are substantially immiscible. If desired two extraction towers maintained at different temperatures may be employed. The paraffinic extract is drawn off, and the solvent removed by evaporation under reduced pressure, leaving a paraffinic oil suitable for use as lubricating oil. The naphthenic oil is obtained in a similar manner. The oil may be dewaxed, and further treated with sulphuric acid and clay. The deposition of wax during the extraction process may be prevented by adding a proportion of the oil obtained by the extraction process. Other suitable combinations of solvents are: propane, together with one of the following: benzaldehyde, nitro toluene, pyridine, or nitrobenzene containing sulphur dioxide.