Relationships between physical properties and chemical constitution of lubricating oil fractions

Abstract

A correlation of the physical properties of a series of petroleum fractions in the lubricating-oil region with each other and with the physical properties of synthetic hydrocarbons of high molecular weight has been made. The petroleum fractions had been extensively separated by distillation and extraction and their empirical formulas determined. The following properties were compared: densities, specific refractions, optical activities, specific dispersions, viscosities, viscosity indices, aniline points, and boiling points.

Extract Portion of the Lubricant Fraction from a Mid-continment Petroleum Hydrogenation

“…Vlugter, Waterman, and Van Westen (17) have shown that the Lorentz-Lorenz specific refractions may be used for determining the number of rings in aromatic-free oils and conversely, for determining whether an oil is aromatic-free by comparing its x value obtained from the carbon and hydrogen ratio-i and molecular weight with that obtained from its specific refraction. This latter method was used in this laboratory with the waterwhite oil (10) and the hydrogenated fractions prepared from the series under discussion (12). In Figure 5 theoretical curves, similar to those of Vlugter, Waterman, and Van Westen (17), show the variation in specific refraction with the number of carbon atoms for paraffins and for naphthenes containing 1, 2, 3, and 4 rings.…”

Exhaustive fractionation of the "extract" portion of the lubricant fraction from a midcontinent petroleum

“…Treatment of the oil at this Bureau has been described elsewhere [1,2,3] and is illustrated diagrammatically in figure 1. It consisted in (1) The separation of an extract portion by extraction with liquid sulfur dioxide at room temperature, (2) the separation of a "wax" portion by crystallization from ethylene chloride at -18° C, and (3) the separation of the remainder into two portions by filtration through silica gel: (a) a water-white portion, whose investigation has already been reported [1,2], and (b) a portion recovered from silica gel and listed in figure 1 as silica gel hold-up.…”

“…In general, the same methods of determining the physical constants were used as with the water-white oil [1,2]. However, complications were introduced in many cases by the extreme viscosity of some of the fractions, their high temperature coefficients of viscosity, their color, and by the fact that they contained sulfur and nitrogen.…”

“…The refractive dispersions are believed to cover about the same range of precision, that is, from ±0.0003 to ±0.0001. In the work with the water-white oil [2], values for the Lorentz-Lorenz specific dispersion (n~-1)/(n~+2) -(n~-1)/(n~+2)X1/d were computed from the values for np-nc given by the Abbe refractometer. This was done to be consistent, since the Lorentz-Lorenz expression (n~-1)/(n~+2) X l/d (desired because of its use in determining the number of naphthene rings per molecule, as described by Vlugter, Waterman, and Van Westen [10]) had been used for the specific refraction.…”

“…Two years ago this laboratory reported the results of an investigation [1,2]3 of the chemical composition of a "water-white" oil prepared from the lubricant fraction of a midcontinent petroleum. To obtain a more complete picture of the whole lubricant fraction of petroleum, a similar investigation has been made on portions of the same fraction which were soluble in sulfur dioxide and retained by silica gel.…”