Attachment of Iron Oxide Nanoparticles to Carbon Nanotubes and the Consequences for Catalysis

Abstract

The attachment of colloidal iron-oxide nanoparticles (designated Fe-NPs) to pristine and surface-oxidized carbon nanotubes (CNTs and CNT-Ox, respectively) was investigated. The loadings of Fe-NPs (size 7 nm) on the CNT and CNT-Ox supports amounted to 3.4 and 2.3 wt. %, respectively; the difference was attributed to weaker van der Waals interactions between the colloidal Fe-NPs and the surface of CNT-Ox. Fischer–Tropsch to olefins (FTO) synthesis was performed to investigate the impact of support functionalization on catalyst performance. Weak interactions between the Fe-NPs and the CNT-Ox support facilitated particle growth and led to substantial deactivation of the Fe/CNT-Ox catalysts. The addition of promoters (Na+S) to Fe/CNT resulted in remarkable activity, selectivity to lower olefins, and stability, making colloidal iron nanoparticles on pristine CNTs a suitable catalyst for FTO synthesis.