Influence of reduction conditions on structure of Fe/TiO2 catalyst for hydrogenation of carbon dioxide

The titania-supported Fe catalyst samples, prepared by incipient wetness impregnation followed by reduction in hydrogen at different temperatures, have higher activity for synthesis of light hydrocarbons from carbon dioxide and hydrogen. The catalytic activity of the catalyst and the product distribution are distinctly affected by the pre-reduction temperature. The best result over 5% Fe/TiO2 reduced in H-2 at 773 K for 5 h shows 19.1% of CO2 conversion with 50.1% of C(2)similar toC(5) selectivity. XRD, laser Raman spectroscopy, Fe-57 Mossbauer spectroscopy and Fe K-edge EXAFS analyses were employed to study the structure of the catalyst. Superparamagnetic Fe-0, alpha -Fe, coordinatively unsaturated Fe2+ (A) cations and the Fe2+ (B) cations in FeTiO3 phase are present in the catalyst, and the catalyst surface is in oxygen-vacancy state. Under an optimum reduction in hydrogen at 773 K for 5 h, the synergy of both zerovalent iron and coordinatively unsaturated Fe2+ (A) cation is thought to be responsible for the higher activity of the catalyst.