The effects of support properties including pore size, hydroxyl group concentration, and support stabilizer were investigated for six alumina-supported FeCuK Fischer-Tropsch catalysts containing 20% or 40% iron. Catalysts were supported on one of four aluminas stabilized with La2O3 or SiO2. A large pore support was found to accommodate 40% Fe without pore blockage. Catalyst activity was found to increase with increasing support pore size, lower OH group concentrations, and higher extents of reduction. SiO2 was found to be a more effective hydrothermal stabilizer than La2O3 as it suppresses the high-temperature transformation of gamma-Al2O3 to alpha-Al2O3 up to 1200 degrees C allowing SiO2-stabilized catalysts to be dehydroxylated at higher temperatures. SiO2 stabilization also inhibits deactivation by sintering and increases activity, possibly due to surface silicate groups. Indeed, the activity of Fe/Si-Al2O3 continues to increase after 700 h on stream, while the Fe/La-Al2O3 catalysts lose activity over the same time period. (C) 2014 Elsevier Inc. All rights reserved.