In lubricating oil fractions

Burdett, R.A., L.W. Taylor and L.C. Jones Jr (1955), Determination of aromatic hydrocarbons in lubricating oil fractions by far UV absorption spectroscopy , p. 30. In Molecular Spectroscopy Report Conf. Institute of Petroleum, London. 

Hood, Clerc and O Neal [13] also discussed the nature of the alkyl chains in lubricating oil fractions. Whereas petroluem waxes are mostly n-alkanes with some isoalkanes and substituted cycloalkanes, the alkanes... 

The crystallization of wax from lubricating oil fractions makes better oil. This is done by adding a solvent (often a mixture of benzene and methyl ethyl ketone) to the oil at a temperature of about -5 F. The benzene keeps the oil in solution and maintains fluidity at low temperature the methyl ethyl ketone acts to precipitate the wax. Rotary filters deposit the wax crystals on a sp woven cloth stretched over a perforated cylindrical drum. A vacuum in the drum draws the oil through the perforations. The wax crystals are removed from the cloth by metal scrapers and ol vent-washed to remove oil followed by solvent distillation to remove oil for reuse. 

Middle distillate one of the distillates obtained between kerosene and lubricating oil fractions in the refining processes. These include light fuel oils and diesel fuels. 

Because the paraffin and mixed-base crudes yield lubricating oil fractions of high quality, means had to be devised in the early days of the petroleum industry to separate the wax from the oil. The removal of wax from petroleum fractions is one of the most important phases in the production of lubricating oils and fuel oils of low pour point, and has received the attention of many investigators. 

The asphaltenes are nonvolatile and remain in the residue when the crude is subjected to distillation. The resins are partially volatile and therefore may be present in the lubricating oil fractions of higher boiling point as well as in the residue. Among the many methods employed for the separation of these materials from the oil fractions are distillation, adsorption, chemical treatment, and precipitation by special solvents. 

A number of special vacuum distillation processes have been developed, whereby thermal decomposition of the oil is kept to a minimum. One of these employs thin film vaporization, in which mercury vapor is employed as an indirect heating medium (89, 71). Another employs a carrier other than steam—for example, kerosene—in the vaporization of the heavy lubricating oil fractions (16). These processes are being operated on a commercial scale, but apparently because of their special nature they have not been widely adopted by the petroleum industry. 

Lillard, Jones, and Anderson (29) in 1951, relating to the types of hydrocarbons in the lubricating oil fraction of a mid-continent and a Gulf Coast petroleum... 

The development of vacuum distillation provided the means of separating lubricating oil fractions with predetermined viscosity ranges and removed the hmit on the maximum viscosity that might be obtained in distillate oil. Vacuum distillation prevented residual asphaltic material from contaminating lubricating oils but did not remove other undesirable materials such as acidic components or components that caused the oil to thicken excessively when cold and become very thin when hot. 

Rossini, Hill, and others have pointed out the great difficulties which will be encountered in isolating and identifying the hydrocarbon in the gas oil, lubricating oil fraction, and wax cut of the crude. Hill, in his paper (55), lists the following means at our disposal for tackling this problem ... 

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