Molecular approaches towards mixed metal oxides and their behaviour in mixed oxide support Au catalysts for CO oxidation

We herein report a water-based sol–gel approach towards porous mixed Si/Ti oxides using co-precipitated glycol-modified precursors. By adjusting synthesis parameters such as the pH value and the Si/Ti ratio of the precursor, the morphology as well as the Si/Ti-composition of the resulting mixed oxide particles can be varied in a wide range. The behaviour of the mixed oxides as substrates for Au catalysts and the performance of the resulting catalysts in the CO oxidation reaction was investigated and compared to catalysts supported on mesoporous anatase and rutile synthesized analogously. For comparable Au particle sizes and Au loadings, the composition of the mixed oxide support was found to significantly affect the reactivity and reaction behaviour, with mixed oxide supported Au catalysts synthesized at pH = 5 or 10 and with a Si/Ti-ratio of 1 : 19 and 1 : 34 exhibiting the maximum activity. In contrast to the enhanced activity, the mixed oxide supports do not lead to a significant improvement in deactivation behaviour and catalyst stability.