The application of inelastic neutron scattering to investigate CO hydrogenation over an iron Fischer–Tropsch synthesis catalyst

Abstract

An iron Fischer–Tropsch (F–T) catalyst has been prepared and evaluated using CO hydrogenation at 623 and 723 K as a test reaction. Micro-reactor measurements establish reaction profiles. The reaction is then scaled up to enable inelastic neutron scattering (INS) measurements of the catalyst to be acquired. The INS spectra (200–4000 cm-1) are characterised by a combination of hydrocarbon moieties and hydroxyl groups. Whereas the low temperature sample is characterised by an aliphatic overlayer, the hydrocarbon features of the high temperature sample are attributed to partially hydrogenated polycyclic aromatic compounds. The catalyst is further characterised by a combination of temperature-programmed oxidation, powder X-ray diffraction, Raman scattering and transmission electron microscopy. This series of measurements is combined to propose a model for the composition of the catalyst as it progresses from the precursor state to steady-state operation. The work features some of the challenges associated with using INS to characterise heterogeneously catalysed reactions systems.