The effect of cobalt and zinc precursors on Co (10%)/Zn (x%)/TiO2 (x=0, 5) Fischer-Tropsch catalysts

A series of Co (10%)/Zn (x%)/TiO2 (x = 0, 5) catalysts were prepared from different nitrate and acetate precursors. TPR and chemisorption techniques revealed that a mixture of cobalt precursors (cobalt acetate and cobalt nitrate) on titania were more easily reduced when compared to Co (10%)/TiO2 catalysts prepared from either cobalt acetate or cobalt nitrate alone. By contrast, after addition of zinc, catalysts prepared from zinc acetate and cobalt nitrate had the most highly dispersed cobalt species when compared to catalysts prepared from the other combinations of nitrate and acetate precursors of zinc and cobalt. Mixed precursors of zinc and cobalt were also more active and had higher CO conversion in Fischer-Tropsch synthesis (FTS) when compared to catalysts prepared from: (i) both nitrate precursors or (ii) both acetate precursors of zinc and cobalt. However, the catalyst prepared from zinc nitrate and cobalt nitrate produced more wax (>C-16) when compared to the other catalysts studied (50% versus 12-32% wax). Data suggest that larger Co particles correlate with wax production as well as reduced CO conversion. CO chemisorption data correlated better with the FT activity data than did Co XPS data. (C) 2004 Elsevier B.V. All rights reserved.