Sol-gel synthesis, characterization, and catalytic activity of Fe(III) titanates

Nanostructured iron-titanium mixed oxides with different Fe/Ti ratios were prepared by sol-gel methods under different preparative conditions. When equal molar amounts of Fe and Ti ions were employed, the product calcined at 500 °C showed an X-ray diffraction pattern that resembles Fe2Ti3O9. On the other hand, lower Fe/Ti ratios favored the formation of Fe2TiO5 while higher ratios resulted in free α-Fe2O3 and TiO2. Besides the effect of the Fe/Ti ratio, the composition of the final product was dependent on the preparative conditions and the calcination temperature. Enhancing the gelation process by heating or by employing an acid catalyst favored the formation of Fe2TiO5 at relatively low temperatures. Compared with the corresponding pure oxides, the prepared iron-titanium mixed oxides showed modified textural characteristics which were also dependent on the composition and the calcination temperature. The mixed oxides showed higher catalytic activity in the oxidation of methanol than their corresponding pure oxides with a noticeable enhanced oxidation potential forming methyl formate and carbon dioxide.