Recovery of Rhenium from Superalloy Scrap

Due to the limited amount of rhenium present in the earths crust (approximately 1-2 part per billion) there is a significant benefit to be realized in recovering for reuse the rhenium from scrap material, spent catalysts, or end-of-life superalloys. Rhenium is found in molybdenum-copper porphyry deposits. If rhenium is present in ore that is processed, it will show up in the resulting molybdenum concentrate and will be retrieved in the molybdenum roasting process. Since there are no primary deposits of rhenium, the method in which it is processed is directly related to method in which molybdenum is produced. Very little rhenium is actually processed and isolated each year as compared to the millions of tons of copper and millions of pounds of molybdenum that are extracted from the same copper deposits. Opportunities exist for enhancing rhenium yield through technological improvements in discrete steps in the recovery process. Due to rheniums excellent high temperature properties (high creep resistance, high melting point, etc.) it is widely used as an alloying agent for high temperature applications including: Pt-Re petroleum reforming catalysts (20% current market use) Super alloys in high temperature turbine engines (70% current market use) Electromagnets, thermocouples, x-ray tube targets, and various others (10% current market use) As of 2010, the USGS reports that all platinum-rhenium petroleum reforming catalysts are recycled [1]. Information on the recycling rates of the remaining 80% of rhenium products is quite limited, although it is postulated to be sufficiently lower than the Pt-Re catalyst industry. Thus, the largest area for potential research may be the recovery and subsequent reuse of the rhenium in superalloys and various rhenium containing products.