No abstract

Interactions between metal nanoparticles and support materials can strongly influence the performance of catalysts. In particular, reducible oxidic supports can form suboxides that can decorate metal nanoparticles and enhance catalytic performance or block active sites. Therefore, tuning this metal-support interaction is essential for catalyst design. Here, we investigate reduction-oxidation-reduction (ROR) treatments as a method to affect metal-support interactions and related catalytic performance. Controlled oxidation of pre-reduced cobalt on reducible (TiO2 and Nb2O5) and irreducible (α-Al2O3) supports leads to the formation of hollow cobalt oxide particles. The second reduction results in a twofold increase in cobalt surface area only on reducible oxides and proportionally enhances the cobalt-based catalytic activity during Fischer-Tropsch synthesis at industrially relevant conditions. Such activities are usually only obtained by noble metal promotion of cobalt catalysts. ROR proves an effective approach to tune the interaction between metallic nanoparticles and reducible oxidic supports, leading to improved catalytic performance.

a Iron-based metal-organic frameworks (MOFs) with varying porosity are converted by pyrolysis into iron/carbon catalysts with predetermined composition and tailored pore structural features for the FischerTropsch synthesis of lower C 2 -C 4 olefins. Significantly higher activity arises for catalysts with higher porosity and decreased iron particle size derived from hierarchical MOF xerogel/aerogel precursors as compared to a purely microporous MOF. Post-synthetic functionalization using sodium and sulfur promoters further enhances the catalytic properties.