Abstract: A process for controlling the removal rate of an aromatic extract oil from a solvent recovery zone in response to the specific gravity of the aromatic extract oil product.

Abstract: An improved solvent extraction process is described for the preparation of lube oil products, the improvement whereby the solvent contains an additive which facilitates phase separation and increases the yield of raffinate.

Abstract: A method is disclosed for reducing the nitrogen content of shale oil using mild hydrogenation followed by liquid sulfur dioxide extraction of the hydrogenated shale oil. The mild hydrogenation is effective for increasing the fraction of shale oil that is insoluble in the liquid sulfur dioxide. The mild hydrogenation is sufficient for saturating unsaturated compounds present in the shale oil to the substantial exclusion of adding hydrogen to the nitrogen of the nitrogen-containing compounds. Following hydrogenation of the shale oil, it is extracted with liquid sulfur dioxide at a temperature from about 14.degree. F. to about 60.degree. F. forming two fractions, a liquid sulfur dioxide insoluble fraction containing a relatively low nitrogen content and a liquid sulfur dioxide soluble fraction containing a relatively high nitrogen content. The liquid sulfur dioxide fraction is separated from the insoluble shale oil fraction. The liquid sulfur dioxide can be recovered for recycling to another extraction step.

Abstract: A method is provided for desulfurization of oil stock, e.g. residual oil, having a minimum sulfur content of about 2 weight percent and a minimum metals content of about 50 ppm to produce a low-sulfur, high-metals content raffinate and a high-sulfur, low-metals content extract which comprises contacting said oil stock with a solvent selective for low molecular weight aromatics and having a boiling point within the range of from about 0.degree. F to about 100.degree. F and a density greater than or less than the density of the oil stock being contacted by at least 0.1 g/cc, said contacting being conducted at a temperature of from about 60.degree. F to about 212.degree. F, a solvent/oil stock volume ratio of from about 0.25 to about 10 and a pressure higher than the vapor pressure of the solvent at the contacting temperature, and separating the low-sulfur, high-metals content raffinate from the high-sulfur, low-metals content extract.