(104a) Nanostructured Ceria and Lanthana for Water-Gas-Shift Catalysis

Advances in materials chemistry over the past decade have opened new possibilities for tailoring the properties of technical catalysts from the nanoscale up. Nanostructured materials, with well-defined morphologies and porosity, i.e. controlled pore diameter and structure, give rise to large and highly accessible internal surface areas, as well as unique properties such as molecular sieving capabilities and/or the capability to integrate multiple functionalities into a single material.

We are reporting on the synthesis, characterization, and testing of nanostructured CeO2- and La2O3-based catalysts for the Water-Gas Shift (WGS) reaction. Target of the present work is the synthesis of nanocomposites by embedding metal nanoparticles on CeO2 and/or La2O3 nanoparticles or nanorods through deposition-precipitation (DP) method. Both oxides have previously been shown to be effective (and active) support materials for noble metal-based catalysts in WGS. However, previous work has mostly focused on the effect of ?nano-sizing? the active metal component in these catalysts, although recent evidence indicates that the structure of the oxide support is much more important than given credit to-date.

The CeO2 and/or La2O3 nanoparticles and nanorods are prepared via two different synthesis routes, a reverse microemulsion-templated sol-gel synthesis and a hydrothermal synthesis, and were characterized by a wide range of methods (SEM, TEM, HRTEM, XRD, BET, and chemisorptions). In this way, we were able to synthesized a range of pure and mixed CeO2- and La2O3-based nanostructured ceramic supports with high surface area and good thermal stability over a broad temperature range of relevance for WGS. By varying different synthesis parameters, both physical (morphology, porosity) and chemical properties (reducibility) of the nanocomposites (pure CeO2 or La2O3, mixed CeO3-La2O3) could be finely tailored by varying different synthesis parameters.

Finally, active metal nanoparticles (Au, Pt, Ni and Cu) were embedded into several of these nanostructured ceramic supports through deposition-precipitation. We found the activity of the catalysts are directly affected by the properties (morphology, reducibility) of the supporting nanostructured oxides.

Synthesis, characterization, and reactive tests will be discussed in detail in the presentation.