(560e) Selective Adsorption of Manganese Onto Cobalt for Optimized Mn/Co/TiO2 Fischer-Tropsch Catalysts

Manganese promoted cobalt Fischer-Tropsch (FT) catalysts have been shown to have higher CO conversion and enhanced selectivity towards C5+ hydrocarbon chains especially when the MnO particles are in close interaction with the Co0, inducing an electronic promotion effect [1]. Until now, controlled intimate contact between the Co0 and MnO particles has proven difficult to achieve, since current synthesis methods often lead to inconsistent and random distribution of the promoter over the catalyst surface.

By controlling the charging parameters of the hydroxyl groups on an oxide support via pH, Regalbuto et al. have shown that a metal complex can be strongly adsorbed on to the oxide surface with high dispersion [2]. Schwarz proposed years ago that one could utilize these electrostatic interactions to direct the adsorption of a metal onto the precursor oxide phase of a supported metal catalyst rather than the support to achieve selective adsorption [3]. Application of this technique can be very beneficial in promoted metal catalysts where intimate contact between the active metal and promoter oxide is of fundamental importance.

This work applies the theory of selective adsorption to the synthesis of Mn/Co/TiO2 FT catalysts by driving the manganese on to the supported Co3O4 phase to achieve systematic catalyst preparation for reaction. Characterization and FT reactivity measurements of these catalysts have presented a more qualitative and quantitative understanding of the effect of manganese on the supported cobalt catalyst. Only a small amount of manganese is necessary to positively enhance the catalytic activity, and through this preparation technique, the required amount of manganese can be placed in close proximity to the active metal.

1. Morales, F., and Weckhuysen, B.M., Catalysis 19, 1 (2006).

2. Regalbuto, J.R. in ?Surface and Nanomolecular Catalysis? (R. Richards, Ed.) Chapter 6 p. 161. Taylor & Francis/CRC Press, Florida, 2006.

3. Schwarz, J.A., Ugbor, C.T., and Zhang, R., J Catal. 138, 38 (1992).