Thin films with a stoichiometry of CeFeOx were conformally deposited on high-surface-area γ-Al2O3 by Atomic Layer Deposition (ALD). X-ray diffraction (XRD) patterns, High-Resolution Transmission Electron Microscopy (HRTEM) images, Raman spectra,...

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In this study, we examined the site and structural requirements for the dehydra-decyclization of cyclic ethers, tetrahydrofuran, and tetrahydropyran to produce conjugated dienes over ZrO2-based catalysts, a reaction that could be an important step in the use of biomass-derived sugars as a starting material to produce monomers for the plastics industry. To help identify the active sites for this reaction, studies were conducted in which ZrO2 surfaces were decorated with Na. These studies showed that Na was effective at poisoning the activity for the ring opening of cyclic ethers, but much less so for the dehydration of the resulting adsorbed alkoxides. The studies of the activity of different types of ZrO2 for the dehydra-decyclization reaction, including single crystals and ultra-thin films supported on MgAl2O4 and silica, also showed that the reaction was dependent on the local structure of the ZrO2 surface. The insights these results provide for identifying the active sites on the ZrO2 surface are discussed.

A 2 nm-thick CeFeO x film was deposited onto γ-Al 2 O 3 by atomic layer deposition (ALD) and then compared to γ-Al 2 O 3 -supported CeO 2 and MgAl 2 O 4 -supported LaFeO 3 films as a catalyst support for Pt. Scanning transmission electron microscopy (STEM) demonstrated that the CeFeO x film uniformly coated γ-Al 2 O 3 , while X-ray diffraction (XRD) indicated that the film reversibly underwent a transition from a fluorite structure following oxidation to a perovskite structure after reduction at 1073 K. A 3.3 wt % Pt/CeFeO x /γ-Al 2 O 3 catalyst showed large (∼10 nm) Pt particles after oxidation at 1073 K, but the Pt dispersed uniformly over the support after reduction at 1073 K. While Pt/CeO x /γ-Al 2 O 3 exhibited high rates for CO oxidation and the water gas shift (WGS) reaction after either oxidation or reduction at 1073 K, reaction rates for Pt/CeFeO x /γ-Al 2 O 3 and Pt/LaFeO 3 /MgAl 2 O 4 depended strongly on the pretreatment conditions. Similar to Pt/LaFeO 3 /MgAl 2 O 4 , oxidized Pt/CeFeO x /γ-Al 2 O 3 exhibited significantly lower rates than Pt/CeO x /γ-Al 2 O 3 for CO oxidation, while reduced Pt/CeFeO x /γ-Al 2 O 3 exhibited much higher CO oxidation rates. While reduced Pt/CeFeO x /γ-Al 2 O 3 was relatively inactive for WGS, oxidized Pt/CeFeO x /γ-Al 2 O 3 was nearly 10 times more active than Pt/CeO x /γ-Al 2 O 3 . Based on these results, the potential implications of the support composition and structure are discussed.