Reaction with metal-doped catalyst systems

Catalyst systems for the WGS reaction that have recently received significant attention are the cerium oxides, mostly loaded with noble metals, especially platinum 42—46]. Jacobs et al. [44] even claim that it is probable that promoted ceria catalysts with the right development should realize higher CO conversions than the commercial Cu0-Zn0-Al203 catalysts. Ceria doped with transition metals such as Ni, Cu, Fe, and Co are also very interesting catalysts 37,43—471, especially the copper-ceria catalysts that have been found to perform excellently in the WGS reaction, as reported by Li et al. [37], They have found that the copper-ceria catalysts are more stable than other Cu-based LT WGS catalysts and at least as active as the precious metal-ceria catalysts. 

Up to now, only a few catalyst systems based on organic polymers such as molybdenum compounds supported on benzimidazole, polystyrene, or poly(gly-cidyl methacrylate) [9] as well as micelle-incorporated manganese-porphyrin catalysts [66] have been tested in the epoxidation of propene. Molybdenum-doped epoxy resins were also employed in the epoxidation of propene with TBHP and propene oxide yields of up to 88% were obtained [65]. The catalysts were employed repeatedly in up to 10 reactions without significant loss of activity and metal leaching proved to be very low. 

The results obtained in this work indicate that the selectivity of platinum catalysts for the hydrogenation of unsaturated carbonyl compounds can be markedly improved by doping the carrier with a monolayer of transition metal ion. It is also worth to note that sandwich-type catalysts (ZrC>2/Pt/Zr02/Ti02) are also active and selective in the studied reaction. We believe that on the surface of this system, the end-on adsorption of aldehyde molecule has been forced. 

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