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: The separation of butadiene-1,3 from other C-4 hydrocarbons of lesser degree of unsaturation by extractive distillation with alkoxynitrile or aqueous alkoxynitrile as selective solvent is carried out with improved selectivity, without appreciable formation of butadiene-1,3 polymer and with consequent savings in energy by adding to the alkoxynitrile or aqueous alkoxynitrile an organic cosolvent which is dimethyl sulfoxide, sulfolane, butyrolactone, N-methyl pyrrolidone, morpholine, or trimethyl phosphate and/or an inhibitor which is 2,4-dinitrophenol or 2,4-dinitro-ortho-cresol. The organic cosolvent is present in the selective solvent composition in an amount of 5 to 30 percent by weight and the inhibitor in an amount of 0.05 to 0.6 percent by weight.

Abstract: Formation of butadiene-1,3 polymer during the extractive distillation of a C-4 hydrocarbon mixture to separate and purify butadiene-1,3 using a solvent composition in which an alkoxynitrile is present in a proportion of 50-99 percent by weight, is decreased through inclusion in the solvent of a synergistic combination of 2,4-dinitrophenol and phosphoric acid, each in a proportion of 0.05 to 0.5 percent by weight.

Abstract: Petroleum fractions may be separated into aromatic rich and paraffinic-rich hydrocarbon streams by the use of methanol/water mixtures having at least 10% water by volume. The paraffinic-rich stream is recovered as raffinate and the aromatic-rich as extract. After the extraction step additional water is added to the extract and raffinate streams where it acts as an anti-solvent to effect separation of the hydrocarbon from the solvent. The water and methanol are then separated for example by flash distillation or by using super critical CO.sub.2 as an extraction solvent.

Abstract: A mixture of C.sub.4 -hydrocarbons is extractively distilled with sulfolane and acetone or methylethyl ketone as the selective solvent; the rich solvent containing 1,3-butadiene and vinylacetylene is stripped and a small quantity of the ketone is allowed to leave overhead. Thereby the further fractionation of the stripper overhead results in a very efficient separation of 1,3-butadiene and vinylacetylene.

Abstract: Isobutene is separated from a charge hydrocarbon stream, which may contain butadiene, in two stages in the first of which isobutene is present in excess and in the second of which isobutene is present in deficiency. In the first stage, a strongly acidic ion exchanger is used and in the second stage, an exchanger with a less powerful H.sup.+ loading is used.