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 degrees C showed an X-ray diffraction pattern that resembles Fe(2)Ti(3)O(9). On the other hand, lower Fe/Ti ratios favored the formation of Fe(2)TiO(5) while higher ratios resulted in free alpha-Fe(2)O(3) and TiO(2). 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 Fe(2)TiO(5) 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. (C) 2009 Elsevier B.V. All rights reserved.