The preparation and characterisation of iron and vanadium oxide monolayer catalysts on TiO₂ and ZrO₂

Iron oxide and vanadium oxide monolayer catalysts have been made by reacting toluene solutions of the corresponding acetylacetonates with the surface OH groups of TiO₂ or ZrO₂. The product of the reaction, acetylacetone, competes with the acetonates for the adsorption sites. Of the four adsorption methods attempted, continuous adsorption and high-temperature adsorption gave approximately complete monolayers; the latter is the more promising method as it is more rapid and consumes fewer chemicals. TPR and CO-oxidation measurements for the Fe₂O₃-TiO ₂ samples show that the monolayer is well-spread and that there is a signficant interaction with the support. The iron cannot be reduced beyond the Fell state, possibly due the formation of a surface ilmenite. The Fe ₂O₃ monolayers are less active for CO oxidation than is bulk Fe₂O₃ Impregnaton of TiO₂ by Fe(NO ₃) gives rise to small crystallites of Fe₂O₃ which have higher actvities for CO oxidation than do the monolayer materials.