Skipped diynones, efficiently prepared from biomass -derived ethyl lactate, undergo a tandem hydra-tionoxacyclization reaction under gold(I)-catalysis. Reaction conditions have been developed for a switchable process that allows selective access to 4-pyrones or 3(2H)-furanones from the same starting diynones. Further application of this methodology in the total synthesis of polyporapyranone B was demonstrated.

By depositing ceria on the surface of yttrium-stabilized zirconia (YSZ) nanocrystals and further activation under high-temperature reducing conditions, a 13% mol. CeO2/YSZ catalyst structured as subnanometer thick, pyrochlore-type, ceria-zirconia islands has been prepared. This nanostructured catalyst depicts not only high oxygen storage capacity (OSC) values but, more importantly, an outstandingly stable redox response upon oxidation and reduction treatments at very high temperatures, above 1000 °C. This behavior largely improves that observed on conventional ceria-zirconia solid solutions, not only of the same composition but also of those with much higher molar cerium contents. Advanced scanning transmission electron microscopy (STEM-XEDS) studies have revealed as key not only to detect the actual state of the lanthanide in this novel nanocatalyst but also to rationalize its unusual resistance to redox deactivation at very high temperatures. In particular, high-resolution X-ray dispersive energy studies have revealed the presence of unique bilayer ceria islands on top of the surface of YSZ nanocrystals, which remain at surface positions upon oxidation and reduction treatments up to 1000 °C. Diffusion of ceria into the bulk of these crystallites upon oxidation at 1100 °C irreversibly deteriorates both the reducibility and OSC of this nanostructured catalyst.

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In this work, copper and cobalt oxides supported on a ceria-yttria-stabilized zirconia (Ce-YSZ) have been studied as alternative to noble metals for the soot removal in diesel engines. The Ce-YSZ support was activated in order to obtain a catalyst with a high redox performance. The resulting catalysts were characterized by N2 physisorption, ICP, XRD, TPR-H2, TPR-CO, HAADF-STEM and XEDS.Additionally, their catalytic performance was evaluated in the NO oxidation to NO2 and in the combustion of soot in presence/absence of NOx. The Co/Ce-YSZ catalyst shows a maximum NO2 production activity higher than 70%, very close to that obtained with a commercial Pt catalyst used as a reference, and largely better than that of Cu/Ce-YSZ. A similar trend is observed in the combustion of soot in the presence of NOx, thus indicating the prevalence of the NO2-assisted mechanism for the oxidation of soot when NO2 is present. Results obtained with unsupported Co3O4and CuO oxides suggest that Co-containing catalyst is not only a better NO2 generator but also exhibits a more efficient utilization of NOx. Co3O4 entities would act as a pseudo-platinum phase allowing fresh supply of NO2 along the catalytic bed, thus accelerating the soot combustion reaction.However, if NOx is absent, the order of soot combustion rate matches with the performance in reducibility ("active oxygen" mechanism), the Cu catalyst being the most active in comparison with Co or Pt. Under these conditions, Ce-YSZ supported catalysts benefit from the excellent oxygenexchange properties of surface Ce-Y-Zr oxide nanostructures.

A nickel-ceria-yttria stabilized zirconia (Ni-CYSZ) cermet material was synthesized and tested as the anode for the direct oxidation of methane in a solid oxide fuel cell (SOFC) with YSZ as the electrolyte and strontium-doped lanthanum manganite (LSM) as the cathode. Initially, the electrochemical behavior was investigated under several load demands in wet (3% H2O) CH4 at 850 °C during 144 h using I-V curves, impedance spectra, and potentiostatic measurements. Long-term tests were subsequently conducted under 180 mA·cm–2 in wet CH4 for 236 h and dry CH4 for 526 h at 850 °C in order to assess the cell stability. Material analysis was carried out by SEM-EDS after operation was complete. Similar cell performance was observed with wet (3% H2O) and dry CH4, and this indicates that the presence of water is not relevant under the applied load demand. Impedance spectra of the cell showed that at least three processes govern the direct electrochemical oxidation of methane on the Ni-CYSZ anode and these are related to charge transfer at high frequency, the adsorption/desorption of charged species at medium frequency and the non-charge transfer processes at low frequency. The cell was operated for more than 900 h in CH4 and 806 h under load demand, with a low degradation rate of ~0.2 mV·h–1 observed during this period. The low degradation in performance was mainly caused by the increase in charge transfer resistance, which can be attributed to carbon deposition on the anode causing a reduction in the number of active centers. Carbon deposits were detected mostly on the surface of Ni particles but not near the anode/electrolyte interface or the cerium surface. Therefore, the incorporation of cerium in the anode structure could improve the cell lifetime by reducing carbon formation.