Improved methods for the selective isolation of the sulfide and thiophenic classes of compounds from petroleum

Abstract

These methods are based on the ability to selectively oxidize the sulfur atom in the two different chemical environments and the large difference in polarity between the oxidized and unoxidized forms. The reagent tetrabutylammonium periodate in toluene/methanol will oxidize the sulfides to highly polar sulfoxides in high yield without affecting the thiophenic compounds. A subsequent chromatographic step permits the isolation of a polar fraction containing the sulfoxides. Reduction of this polar fraction regenerates the sulfides, which are isolated by chromatography. The sulfide content was found to vary from 2.6% to 16% of the heavy oils and bitumens of Alberta. A second oxidation of the remaining fraction, after removal of the sulfides, using m-chloroperbenzoic acid under anhydrous neutral conditions converts the thiophenes into their corresponding polar sulfones, which are isolated from the mixture by a subsequent chromatographic step. Reduction regenerates the thiophenic compounds, which are purified again by chromatography. The content of the thiophenic compounds was found to vary from 0.3% to 7.6% of the various conventional oils, heavy oils, and bitumens examined