Effect of type and localization of nitrogen in graphene nanoflake support on structure and catalytic performance of Co-based Fischer-Tropsch catalysts

Cobalt catalysts on carbon-based materials for Fischer-Tropsch synthesis: a review

“…However, these catalysts showed low SC5+, which was assigned to the narrow pore size < 1 nm in the pore structure of oxidized GNF and N-GNF, which hindered CO diffusion and increased H2 diffusion, consequently, limiting the formation of long-chain hydrocarbons [231]. The combination of functional groups such as O or N in the carbon structure decreases the MSI, enhances the Co reducibility and dispersion, and affords good stability to the Co particles [231]. However, the excess of oxygen groups on the N-doped oxidized carbon support improves the CH4 selectivity via the occurrence of the H-spillover [231].…”

“…Among the carbon materials, the ones with a graphitic structure like CNF, CNT, and graphene are the most commonly used as catalyst supports in FTS [217,231,232]. However, their inherent hydrophobic properties and their poor surface reactivity can limit their application as catalyst support, due to a poor interaction with the metallic precursor during catalyst preparation [221].…”

“…In another study, it was also shown that on N-doped graphene nanoflakes (N-GNF), the resistance to Co sintering during catalyst reduction was lower for the support predominantly containing amide groups localized at the edges of graphene layers than for the ones containing pyridones and pyridines/pyrrols/graphitic nitrogen groups [231].It was reported that the pyridine-like sites near carbon vacancies affect the electronic state of cobalt and contribute to the auto-reduction of cobalt oxide of Cо3O4/N-CNF catalysts used for the oxidation of carbon monoxide [108,160,246]. The FTS catalytic tests (T = 240 °C, P = 20 bar,H2/CO= 2, GHSV = 6000 mL g -1 h −1 ) showed that the catalysts prepared on oxidized GNF and N-GNF had the highest activity, as a result of their highest contents of functional groups (O or N), leading to the best Co dispersion and stabilization.…”

“…The FTS catalytic tests (T = 240 °C, P = 20 bar,H2/CO= 2, GHSV = 6000 mL g -1 h −1 ) showed that the catalysts prepared on oxidized GNF and N-GNF had the highest activity, as a result of their highest contents of functional groups (O or N), leading to the best Co dispersion and stabilization. However, these catalysts showed low SC5+, which was assigned to the narrow pore size < 1 nm in the pore structure of oxidized GNF and N-GNF, which hindered CO diffusion and increased H2 diffusion, consequently, limiting the formation of long-chain hydrocarbons [231]. The combination of functional groups such as O or N in the carbon structure decreases the MSI, enhances the Co reducibility and dispersion, and affords good stability to the Co particles [231].…”

“…The combination of functional groups such as O or N in the carbon structure decreases the MSI, enhances the Co reducibility and dispersion, and affords good stability to the Co particles [231]. However, the excess of oxygen groups on the N-doped oxidized carbon support improves the CH4 selectivity via the occurrence of the H-spillover [231]. Two strategies can be used in order to improve the SC5+, while keeping a reasonable catalytic activity during FTS.…”