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NiO−CeO2 and NiO−CeO2−ZrO2 catalysts have been synthesized, electrochemically characterized (Mott‐Schottky (MS) measurements and Electrochemical Impedance Spectroscopy), physicochemically characterized (by N2 adsorption, XRD, Transmission Electron Microscopy and XPS) and tested in the N2O assisted ethane oxydehydrogenation. The use of low Zr‐loadings (Zr/Ce=0.1 at. ratio) has led to the optimal results in the ethylene production, improving those obtained by the Zr‐free NiO−CeO2 catalyst. However, high Zr‐loadings have meant a decrease in the olefin production. The catalytic results obtained have been explained considering the amount of oxygen vacancies, the crystalline phases formed and, especially, the nature of the surface Ni species. Importantly, the use of N2O as an oxidizing agent leads to a remarkable improvement in the selectivity to the olefin compared to that obtained employing molecular O2. Then, for a given ethane conversion the selectivity to ethylene is ca. 15 points higher using N2O than using O2. Another additional positive aspect of this NiO−CeO2−ZrO2 catalyst is its high catalytic stability. [ABSTRACT FROM AUTHOR]

Several CeO2 and CuO-CeO2 catalysts were prepared using different methods, i.e., a homogeneous precipitation with urea, a nanocasting route using CMK-3 carbon as a hard template and a sol-gel process using Poly(methyl methacrylate) (PMMA) polymer as a soft template, and tested in the total oxidation of propane. The catalysts were characterized by a number of physicochemical techniques (XRD, N2 adsorption, TPR, XPS, Raman spectroscopy) showing distinct characteristics. For each series, Cu-Ce-O catalysts with low Cu-loadings (5 wt % CuO) showed the highest activity, higher than those samples either without copper or with high Cu-loading (13 wt % CuO). The incorporation of copper leads to an increase of the concentration of bulk defects but if the Cu-loading is too high the surface area drastically falls. The highest activity in the total oxidation of propane was achieved by Cu-containing ceria catalysts synthesized using a polymer as a template, as this method yields high surface area materials. The surface area and the number of bulk/sub-surface defects of the ceria seem to be the main properties determining the catalytic activity. [ABSTRACT FROM AUTHOR]

Different nickel catalysts have been tested for the transformation of levulinic acid into γ-valerolactone using an easy hydrothermal method, taking advantage of the properties of the high temperature water. A metallic nickel catalyst derived from NiO synthesized by a nanocasting procedure can achieve a productivity to γ-valerolactone, which is two orders of magnitude higher than that obtained by a commercial nickel catalyst. This nanocasted metallic nickel catalyst has shown bifunctionality as it is capable of activating water as the source for hydrogen and undertaking the further hydrogenation step. In contrast with metallic nickel, nickel oxide has shown to be incapable of transforming levulinic acid into γ-valerolactone. [ABSTRACT FROM AUTHOR]