In collaboration with a major provider of Fischer-Tröpsch synthesis (FTS) catalytic technology, the research team have recently demonstrated how INS can be used to probe iron based FTS catalysts. This has necessitated refinements in sample environment at the Central Facility, with the studies providing new information on the operational phase of these important catalytic materials. Against this background, it is proposed to evaluate the effectiveness of INS in providing information on an ¿evolutionary¿ phase of the catalyst conditioning process that is associated with variable rates of reaction. Monitoring of the INS spectrum of iron based FTS catalysts as a function of extended time-on-stream will make full use of the improved sample environment capability.