(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.