Stability and structure of cobalt catalytic systems in fischer-tropsch synthesis: supercritical fluid media versus conventional gas-phase media

The sensitivity of the supported-cobalt catalyst structure (physicochemical characteristics, oxidation states, and crystalline structure of the active phase) during the Fischer-Tropsch synthesis (FTS) reaction was studied. Three catalytic systems were tested under both conventional gas-phase and supercritical phase FTS (15% Co/SiO2 HSA supported on high surface area silica, 15% Co/SiO2 LSA supported on low surface area silica, and 15% Co/Al2O3). In situ reducibility of the cobalt oxide took place during the FTS reaction in both gas-phase FTS and SCH-FTS conditions. In the latter, the in situ reduction of Co3O4 gave active crystal-lines of hcp and fcc Co0 that were very stable for a long TOS. As a result, the activity and selectivity of the catalyst in the SCH medium was more stable and recoverable than that under gas-phase FTS conditions. The in situ reduction pathway of the silica supported catalyst was different than that of the alumina supported one. However, a stable form of fcc Co0 was also detected on the used catalyst from the SCH-FTS operation. This is an abstract of a paper presented in the ACS Fuel Chemistry Meeting Fall 2005 (Washington, DC Fall 2005).

Stability and structure of cobalt catalytic systems in fischer-tropsch synthesis: supercritical fluid media versus conventional gas-phase media Conference Paper