Highly active and stable supported iron Fischer–Tropsch catalysts: Effects of support properties and SiO2 stabilizer on catalyst performance

• Effects of support properties on catalyst activity and stability were investigated.
• A support with large pore volume accommodates higher Fe loading without pore blocking.
• Fewer OH groups lead to higher extent of reduction and higher activity.
• SiO2 stabilization inhibits deactivation by sintering and increases activity.
• SiO2 was found to be a more effective hydrothermal stabilizer than La2O3.

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 γ-Al2O3 to α-Al2O3 up to 1200 °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.

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