Citral hydrogenation over Ir/TiO2 and Ir/TiO2/SiO2 catalysts

Catalytic hydrogenation of citral over iridium supported on TiO2, SiO2 and mixed oxides TiO2/SiO2 has been studied. The effect of the reduction temperatures (473 or 773 K) and the successive enrichment of TiO2 were analyzed. The solids were characterized by H-2 chemisorption at room temperature, N-2 adsorption at 77 K, XRD, TEM, FTIR and XPS. The obtained results show that the high temperature reduction treatment (HT) produces an important enhancement in both the catalytic activity and selectivity towards the desired product. The behavior is explained on the basis of a surface enrichment in titania due to the migration of TiOx species on the Ir crystallites, which does not occur in those catalysts reduced at low temperature (LT) or in the catalyst supported on an inert oxide such as SiO2. (C) 2008 Elsevier B.V. All rights reserved.