(441b) Robust Nanostructured Noble Metal/ Ceria/Lanthana Catalysts for Water-Gas-Shift

Noble metal nanoparticles dispersed on oxide supports are widely used as catalysts in fuel processing, chemicals production, and environmental protection. Particularly noble metal/ceria catalyst systems have found much attention due to their excellent activity in partial oxidation and Water-Gas Shift (WGS). However, the noble metal nanoparticles typically suffer from insufficient thermal stability and high sensitivity to poisoning in the presence of S-contamination in the reactor feed. Both sintering due to high temperatures as well as poisoning by S-contaminants result in the loss of active surface area and result in – often irreversible - deactivation.

Here, we are reporting on the synthesis, characterization, and testing of robust nanostructured noble metal catalysts (La-Au-Ce and La-Pt-Ce) in Water-Gas Shift with S-contaminated syngas feeds. The metal nanoparticles are deposited on nanostructured CeO₂ via through deposition-precipitation or impregnation. Subsequently, the supported catalysts were decorated with a La₂O₃ overlayer. This protective overlayer results in enhanced thermal stability of the catalyst, and shields the active metal from S-poisoning while simultaneously enabling the catalyst to capture sulfur, as lanthana is known to be an efficient regenerative S-capturing material in the temperature range of interest in WGS. The nanostructured CeO₂ support then facilitates the fast regeneration of the noble metal nanoparticles in the reducing atmosphere.

The catalyst were characterized (TEM, XRD, BET, and TPO/TPR), and tested in cyclic fixed-bed reactor experiments. WGS activity test in repeated temperature ramps shows greatly improved stability of the active nanoparticle through the surface decoration. The results in repeated sulfidation-regeneration cycles are equally promising, showing fast sulfur uptake kinetics, large S-capturing capacity, and stable regeneration. Overall, the carefully controlled nanostructure hence results in a highly efficient and stable multifunctional catalyst material. Synthesis, characterization, and catalytic activity tests will be discussed in detail in the presentation.