Supercritical Activity Restoration for Fischer Tropsch Synthesis

Abstract

Previous research has demonstrated that supercritical phase Fischer Tropsch Synthesis (SC-FTS) using hexanes as the solvent medium offers superior activity maintenance to traditional fixed-bed (gas phase) Fischer Tropsch Synthesis (GP-FTS) (Elbashir et al., 2005). This has prompted an investigation into whether supercritical media can reactivate a catalyst used in GP-FTS. To that end, a study was conducted in which a series of GP-FTS experiments of approximately 2 days each were performed, separated by in situ periods of catalyst reactivation using supercritical hexanes as well as SC-FTS.It was found that the supercritical hexanes media and SC-FTS reactivation periods were effective in partially restoring lost catalyst activity and selectivity. GP-FTS was demonstrated to have detrimental effects on subsequent SC-FTS operation while SC-FTS operation showed beneficial effects on subsequent GP-FTS operation. Specifically, SC-FTS reactivations reduced the methane selectivity in subsequent GP-FTS periods. The CO2 selectivity in SC-FTS is consistently lower than that in GP-FTS, while the olefin selectivity into the diesel range is higher in SC-FTS. While the propagation probability was initially higher in SC-FTS than GP-FTS, the propagation probability values converged as the experiment progressed.