Fuel-Rich Combustion Synthesized Co/Al2O3 Catalysts for Wax and Liquid Fuel Production via Fischer–Tropsch Reaction

Alumina supported cobalt catalysts were synthesized for Fischer–Tropsch (FT) reaction using combustion synthesis (CS) method via the redox reaction of hexamethylenetetramine and cobalt nitrate with equivalence ratios (ϕ) of 1, 1.2, and 1.5. Higher equivalence ratios (ϕ > 1.0) were selected to increase the synthesis temperature and thereby decrease the formation of cobalt aluminates. Chemisorption and XPS studies of CS(ϕ = 1.2) and CS(ϕ = 1.5) catalysts showed high degree of reduction, high metal dispersion, and decreased formation of cobalt aluminates compared to CS(ϕ = 1) catalysts. Higher FT activity was observed for catalysts synthesized with equivalence ratios of 1.2 and 1.5 compared to the catalysts synthesized with ϕ = 1. Simultaneously, the hydrocarbon product spectrum shifted from predominantly waxes (C 24+ ) for CS(ϕ = 1) catalysts to mixed fractions of liquid fuel (C 6 –C 24 ) and waxes for CS(ϕ = 1.2) and CS(ϕ = 1.5) catalysts. This work investigates the impact of CS stoichiometry on catalyst properties, in particular the metal support interaction, and its outcome on FT activity and selectivity.