Enhanced Activity via Surface Modification of Fe-Based Fischer–Tropsch Catalyst Precursor with Titanium Butoxide

The surface of a model iron catalyst precursor was modified with titanium butoxide to introduce Fe–O–Ti interactions in a controlled manner and to investigate the role of these interactions in the catalyst. The reduction of the model catalyst precursors in hydrogen at 350 °C for 16 h leads to the formation of α-Fe and an iron–titanium mixed oxide, due to the incorporation of Ti into the iron oxide structure. The α-Fe phase is transformed into χ-Fe 5 C 2 during the Fischer–Tropsch synthesis at 250 °C, whilst the Fe–Ti mixed oxide phase is preserved. A higher reaction temperature of 300 °C is required to transform some the oxide phase into a carbide phase under Fischer–Tropsch conditions. The intrinsic activity of the iron carbide phase in samples also containing the Fe–Ti mixed oxide phase is at a reaction temperature of 250 °C ca. 20 % more active than in the sample, which does not contain the mixed oxide.