Impact of impregnation sequence on the structure of CoPt/Nb2O5 Fishcer-Tropsch catalysts on the same dispersion basis

Three Nb 2 O 5 supported Pt-promoted cobalt catalysts were prepared by co-impregnation and sequential impregnation methods. The dispersion of cobalt species was controlled by glow discharge plasma technique, and cobalt particle size on all three catalysts are in the same level (4.2–4.6 nm). It was found that the metal precursor impregnation sequence significantly affected the interaction among Co, Pt and Nb 2 O 5 , and thus results in different H 2 adsorption capacity. Compared to the catalyst prepared by first impregnation of Pt precursor (Pt-Co/Nb 2 O 5 ), the catalysts prepared by simultaneous impregnation of Co and Pt precursors (CoPt/Nb 2 O 5 ) and first Co impregnation (Co-Pt/Nb 2 O 5 ) obtained a significantly decreased interaction among Co and Nb 2 O 5 . Moreover, high cobalt reducibility (>88 %) was realized at such high cobalt dispersions on these two catalysts, the corresponding weaker H 2 adsorption strength and more active sites resulted in their 1.8 times higher FTS activities than Pt-Co/Nb 2 O 5 .