Xiong H., Motchelaho M.A.M., Moyo M., Jewell L.L., Coville N.J.
DST/NRF Centre of Excellence in Strong Materials, University of the Witwatersrand, Johannesburg 2050, South Africa; Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand, Johannesburg 2050, South Africa; School of Chemical and Metallurgical Engineering, University of the Witwatersrand, Johannesburg 2050, South Africa
Xiong, H., DST/NRF Centre of Excellence in Strong Materials, University of the Witwatersrand, Johannesburg 2050, South Africa, Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand, Johannesburg 2050, South Africa; Motchelaho, M.A.M., Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand, Johannesburg 2050, South Africa, School of Chemical and Metallurgical Engineering, University of the Witwatersrand, Johannesburg 2050, South Africa; Moyo, M., Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand, Johannesburg 2050, South Africa, School of Chemical and Metallurgical Engineering, University of the Witwatersrand, Johannesburg 2050, South Africa; Jewell, L.L., School of Chemical and Metallurgical Engineering, University of the Witwatersrand, Johannesburg 2050, South Africa; Coville, N.J., DST/NRF Centre of Excellence in Strong Materials, University of the Witwatersrand, Johannesburg 2050, South Africa, Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand, Johannesburg 2050, South Africa
A series of Co catalysts supported on carbon nanotubes (CNTs) and carbon spheres (CSs) with different cobalt particle sizes (3-45 nm) were prepared by different methods and using different cobalt precursors. The Co/CNTs and Co/CSs can be autoreduced by the supports in N2 at ca. 480 °C; they show better Fischer-Tropsch performance than those reduced in H2 when the reduction T > 400 °C. The turnover frequency (TOF) value for both Co/CNT and Co/CS was constant for cobalt particles above 10 nm and decreased sharply for the cobalt catalysts with smaller cobalt particles. Remarkably, the TOF for 11 catalysts prepared using different precursors and preparation methods on two different carbon supports depends only on particle size. Finally, a positive relationship was observed between cobalt particle size and C5+ selectivity for both Co/CNT and Co/CS catalysts. © 2010 Elsevier Inc. All rights reserved.