Parametric study of coiled carbon fibre synthesis on an in situ generated H2S-modified Ni/Al2O3 catalyst

Coiled carbon fibre (CCF) synthesis on an in situ generated H2S-modified Ni/Al2O3 catalyst is investigated using a high-throughput reaction system that allows real time observation of weight changes. The influence of reduction and synthesis temperatures, reduction duration, H2 addition during synthesis, synthesis duration, C2H2 concentration in the synthesis gas and catalyst loading are investigated and products are analysed by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy and thermogravimetric analysis. Thermodynamic equilibrium models of various experimental scenarios provide insight into the predominant species present at equilibrium. Reduction temperature and reduction duration affect H2S concentration, a vital parameter for CCF synthesis, and CCFs form in only a narrow reduction and synthesis temperature range of 650 °C ± 50 °C with greatest coil yields observed at 650 °C and following reduction durations of between 1 and 20 min with greatest coil yields observed after a 10 min reduction. The presence of H2 during synthesis was found to have a positive effect on CCF formation. The ratio of thick to thin carbon fibres increased with catalyst nickel loading and the greatest ratio of CCFs was produced with a 1:20 wt. Ni:Al2O3 catalyst.