Atomic-Scale Investigation of the Structural and Electronic Properties of Cobalt–Iron Bimetallic Fischer–Tropsch Catalysts

Abstract

Supported cobalt and iron catalysts are important for many catalytic processes. It is believed that combining both elements in a bimetallic catalyst would result in a synergetic catalytic activity during Fischer–Tropsch Synthesis. However, the nature of the interaction between the two elements and its effect on their catalytic properties are not well understood. In the present work, we report the synthesis of carbon-nanotube-supported Co–Fe alloy catalysts using colloidal chemistry methods. The ratios of Co–Fe and their homogeneous distribution in the supported nanoparticles were confirmed using local and bulk characterization techniques. We observed the formation of Co–Fe Janus-like alloy structure and a change of their elemental distribution at the nanoparticle scale upon reduction. The bimetallic catalyst showed reasonable Fischer–Tropsch catalytic activity and selectivity to C5+ hydrocarbons when compared with monometallic iron and cobalt catalysts. Finally, we found that the active phase of the Co–Fe bimetallic species during catalysis depends on the catalytic conditions.

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

“…In order to avoid aggregation, coalescence, and growth, ligands present in the solution play an essential role in stabilizing the nanoparticles [156]. The main challenge in catalyst preparation by this method is ligands removal, which hamper the accessibility of reactants to the metal surface and thereby limit catalytic activity, especially in FTS [90,180]. In this context, van Deelen et al [90] investigated the effect of oxidative treatments (Figure 23a) on the deposition of cobalt nanocrystals (Co-NC) or (CoO-NC) onto CNT and subsequent ligand removal.…”

Iron and copper nanoparticles inside and outside carbon nanotubes: Nanoconfinement, migration, interaction and catalytic performance in Fischer-Tropsch synthesis

“…In recent years, carbon materials have attracted increasing attention as supports for metal catalysts and demonstrated enhanced selectivity and activity for many reactions. Ironbased catalysts are the catalysts of choice for direct light olefin synthesis via hightemperature Fischer-Tropsch (FT) synthesis [1][2][3]. Iron catalysts show low selectivity to undesirable methane, high water-gas shift activity [4], which can adjust the low H2/CO ratio in syngas obtained from biomass or organic waste.…”

Designing Nanoparticles and Nanoalloys for Gas-Phase Catalysis with Controlled Surface Reactivity Using Colloidal Synthesis and Atomic Layer Deposition

“…The addition of promoting elements is a known strategy for tuning the performance of FTS catalysts [117]. In an approach to study Co-Fe interactions and their effect on FTS performance, Ismail et al [118] prepared monodisperse (5-7 nm) carbon nanotube (CNT)-supported CoFe catalysts via a nonhydrolytic colloidal method. The reduced catalyst displayed partial Janus-like alloy formation ( Figure 7) and had higher activities and selectivities compared to monometallic counterparts.…”

“…Adapted with permission from Ref. [ 118 ], . Further permissions related to the material excerpted should be directed to the ACS.…”