The performance of Co/Nb2O5 was compared to that of Co/γ-Al2O3 for the Fischer–Tropsch synthesis at 20 bar and over the temperature range of 220–260 °C. The C5+ selectivity of Nb2O5-supported cobalt catalysts was found to be very high, i.e. up to 90 wt% C5+ at 220 °C. The activity per unit weight cobalt was found to be similar for Nb2O5 and γ-Al2O3-supported catalysts at identical reaction temperature. However, due to the low porosity of crystalline Nb2O5, the cobalt loading was limited to 5 wt% and consequently the activity per unit weight of catalyst was lower than of Co/γ-Al2O3 catalysts with higher cobalt loadings. This low activity was largely compensated by increasing the reaction temperature, although the C5+ selectivity decreased upon increasing reaction temperature. Due to the high intrinsic C5+ selectivity, Nb2O5-supported catalysts could be operated up to ~250 °C at a target C5+ selectivity of 80 wt%, whereas γ-Al2O3-supported catalysts called for an operation temperature of ~210 °C. At this target C5+ selectivity, the activity per unit weight of catalyst was found to be identical for 5 wt% Co/Nb2O5 and 25 wt% Co/Al2O3, while the activity per unit weight of cobalt was a factor of four higher for the niobia-supported catalyst.
Fischer–Tropsch Niobia Selectivity Reaction temperature
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This research was financially supported by Companhia Brasileira de Metalurgia e Mineração—CBMM. The authors would like to thank Dr. Robson Monteiro and Mr. Rogério Ribas from CBMM for useful discussions and for supplying the niobia samples.