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 (C24+) for CS(ϕ = 1) catalysts to mixed fractions of liquid fuel (C6−C24) 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