Studies on the Removal and Recovery of Organic Sulfur Compounds in Hydrocarbon Oils by Liquid-Liquid Extraction (IV)

In order to develop a new method for removing the sulfur compounds in hydrocarbon oils, the extraction behavior of tetrahydrothiophene (THS) with an aqueous copper (II) bromide solution was investigated with special reference made to the mechanism of extraction and the factors which influence the extraction ability of copper complexes.Bromo-copper (II) complexes exhibited excellent extraction efficiency for THS that was more than 50 times as great as that of cupric ion itself. CuBr+, among the bromo complexes, was mainly concerned with the extraction of THS and it formed a white solid complex having a composition of [Cu(I)Br THS]. This solid complex was redissolved in the presence of excess amounts of Br- ion and/or CuBr2; and, thus, THS was extracted into the aqueous phase as water soluble complexes; i. e., copper (I) complex ions, [Cu(II)BrnTHS](n-1)- (n=2, 3) and/or mixed valance polynuclear complex ions, [Cu(II)-Brn-1-Cu(I)THS](2-n)+ (n=1, 2), respectively. The role of Br- ion as an auxiliary ligand was also discussed.