Bimetallic Rh-Ge and Pt-Ge catalysts supported on TiO2 for citral hydrogenation II.: Catalytic properties

Bimetallic Rh-Ge/TiO2 and Pt-Ge/TiO2 catalysts prepared by surface redox reaction (catalytic reduction method) were tested for the selective hydrogenation of citral. Samples were reduced either at 300 degrees C or at 500 degrees C (SMSI effect). For both Rh and Pt series, the unsaturated alcohols (UA) selectivity goes through an optimum as a function of the germanium content whatever the reduction temperature. For low Ge loadings, it was possible to combine the bimetallic and SMSI effects, inducing a high UA selectivity on bimetallic catalysts supported on TiO2. On the other hand, at high Ge loadings the bimetallic effect was predominant and led also to a high UA selectivity. Moreover, TiO2 support contributed to stabilize the bimetallic Rh-Ge and Pt-Ge particles prepared by catalytic reduction toward an air exposure at ambient temperature. (c) 2006 Elsevier B.V. All rights reserved.