Fischer-Tropsch synthesis: the atmosphere effect in the activation of Fe catalyst supported in SBA-15

FIGUEROA, S. J. A.; S. J. STEWART; L. A. CANO; J. F. BENGOA; S. G. MARCHETTI

Grenoble

Encuentro; Users Meeting ESRF; 2010

ESRF

An iron catalyst supported on a mesoporous solid, named SBA-15,was prepared by incipient wetness impregnation andactivated following two different methodologies, in pure H2stream and in synthesis gas(H2:CO=2:1) stream, in order to be used in the Fischer-Tropsch synthesis. The solids were characterized by atomic absorption spectroscopy, N2 adsorption, X-ray diffraction at low angles, Mössbauer spectroscopy, temperature programmed hydrogenation and in situ X-ray absorption studies at Fe K-edge. Different initial iron species were obtained after the different activation treatments: Fe2+ diffused into the SBA-15 walls, Fe3O4 and Feº for the catalyst activated in pure H2 stream and Fe2+, Fe3O4 and χ- Fe5C2 carbide for the catalyst activated in synthesis gas. The initial “bulk” structural differences would disappear while the catalysts are “working”. However, the catalytic tests showed a higher total hydrocarbon production velocity, a higher CO conversion and a higher selectivity towards light olefins when the activation was made in pure H2 stream. These results would indicate that the inicial differences in the structure of the active sites are maintained during the reaction.