Hydrometallurgical Treatment of Elemental Sulfur in Spent Catalysts by Aqueous and Nonaqueous Solutions at Low Temperature

Abstract

ABSTRACTSpent catalysts generated from petroleum refining contain some valuable metals and their surface is covered by elemental sulfur. During the recovery of valuable metals in the spent catalysts, the sulfur present in the surface of spent catalyst should be treated. In order to develop an environment-friendly process to treat these spent catalysts, the dissolution behavior of elemental sulfur between nonaqueous solvents (octanol/decanol) and NaOH solution was compared, which has never been reported. Sulfur was dissolved in decanol and octanol and the dissolved sulfur was recrystallized as the solution cooled to room temperature. The optimum treatment conditions of sulfur in nonaqueous solvents were obtained. The interaction of sulfur with these nonaqueous solvents was analyzed through a radical mechanism and its mechanism was first proposed in the current work. Unlike the treatment of sulfur with decanol and octanol, the dissolution of sulfur in NaOH solution is assumed to occur through oxidation/reduction reaction and the optimum conditions were obtained. The application of these methods is expected to have a meaningful impact on the recovery of sulfur from spent catalyst materials.