Mesoporous hollow carbon spheres (MHCSs) were synthesized (d = 290 nm; carbon shell 20−35 nm), and their hollow morphology was exploited to study the influence of Ru nanoparticle location relative to Co3O4 nanoparticles on the reduction behavior and activity of Co Fischer−Tropsch catalysts. Ru nanoparticles were loaded both inside and outside the MHCS, while Co3O4 particles (ca. Co 15 wt % loading) were loaded on the outside of the MHCS. The use of in situ powder X-ray diff raction (PXRD) and temperaturepro-grammed reduction studies on the catalysts indicated the eff ect of Ru location on the Co3O4 reduction pathways. A secondary hydrogen spillover eff ect was invoked to explain a complete reduction of the Co3O4 on Ru@MHCS@Co at 450 °C. Secondary hydrogen spillover enhanced the CoO to Co transformation by lowering the reduction temperature when compared to the unpromoted catalyst. Primary hydrogen spillover was inferred to explain the complete reduction of Co3O4 to Co metal on CoRu/MHCS at 300 °C. After catalyst activation at 350 °C, the primary spillover process yielded a catalyst with higher Fischer−Tropsch activity (ca. 2×) than the unpromoted catalyst and the catalysts where Ru and Co were separated by the mesoporous carbon shell. This was partially related to the Co phases that formed on the carbon support during reduction and the catalyst degree of reduction that was reliant on the type of hydrogen spillover process.

Carbon spheres (CSs) synthesised by the hydrothermal approach were explored as a model support material for a bimetallic Fe–Co Fischer–Tropsch (FT) catalyst. The CSs were characterised by N2 adsorption–desorption, thermogravimetric analysis, FTIR spectroscopy and powder XRD. If annealed at 900 °C for 4 h, the CSs exhibited an improved surface area, thermal stability and crystallinity. A series of Fe–Co bimetallic FT catalysts supported on the annealed CSs were prepared by co‐precipitation. A variety of Fe‐to‐Co ratios were used with the total metal loadings maintained at 10 %. Catalyst reducibility studies were performed by H2 temperature‐programmed reduction and in situ powder XRD. Catalysts with a Fe/Co ratio of 5:5 (w/w) showed Co–Fe alloy formation upon reduction at >450 °C. Interestingly, the presence of this alloy did not correlate with high C5+ selectivities during FT synthesis; rather the Co‐rich/Fe‐poor catalyst gave the best selectivity. The CSs allowed the metal–metal interactions in the bimetallic systems to be monitored because of the weak interaction of the metals with the support.

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In this study the outer surface of porous hollow carbon spheres (HCSs) materials were functionalized by N-doping using a post-synthesis method and they were used as a Fischer-Tropsch catalyst support. Melamine was used as the nitrogen source, and carbonization was performed at diff erent temperatures (600 and 900 °C) to introduce variable levels of N into the HCSs, with diff erent bonding configurations. This procedure allowed for the incorporation of up to 13% N. Our results show that post-synthesis N-doping introduced marginal defects into the carbon framework and this did not aff ect the thermal stability of the materials. XPS studies revealed that the surface content on these materials varied and provided evidence for temperaturetunable bonding configurations. Eff ects associated with post-synthesis N-doping were apparent on the Co catalyst (˜10 wt.%) properties such as the inhibited reduction caused by a metal-support interaction observed by the H2-TPR and in situ PXRD techniques. As a consequence the Fischer-Tropsch performance was influenced as both the activity and stability were improved on the catalysts supported on the N-doped materials. TEM analysis of the spent catalysts demonstrated the influence of N-doping on the sintering characteristics of Co, with particles > 30 nm measured on the N-free catalyst while Ndoped samples had sizes < 15 nm.