Reduction of High Surface Area CeO₂−ZrO₂ Mixed Oxides

Abstract

The objective of this study was to examine the mechanism of the reduction by hydrogen of ceria-zirconia (CZ) mixed oxides having a high BET surface area (100 m 2 g -1 ). Three methods were used in parallel to assess the Ce 3+ content, the surface and bulk oxygen vacancy concentrations, and the resulting oxygen storage capacity (OSC): temperature programmed reduction, Fourier transform infrared (FT-IR) measurements of methanol adsorbed on the reduced surfaces, and a Faraday microbalance to determine the magnetic susceptibility of the reduced oxides. The three methods conclude that the introduction of zirconium into the ceria lattice has a positive influence on the OSC. Compared to pure ceria, the CZ mixed oxides exhibit better redox properties, with a lower temperature of initial reduction and a higher reduction percentage for all compositions. The reducibility increases with the zirconium content, however the OSC per gram of solid is practically the same for Zr contents between 20% and 50%. The reduction process very rapidly involves the bulk, but a treatment at room temperature under oxygen of the reduced samples oxidizes them almost completely. However, the FT-IR results underline the differing behavior of ceria for the distinct surface and bulk reduction processes.

Characteristics of Au/HMS catalysts for selective oxidation of benzyl alcohol to benzaldehyde

“…So far mesoporous inorganic oxides are of interest because they exhibit numerous edges and corners for adsorption of reactants and dispersion of noble metal nanoparticles [5,19]. HMS silicas, form a spongelike particle texture through the intergrowth of mesoscopic wormhole framework domains, and have found promising applications as heterogeneous catalysts and as supports for the immobilization of reagents [20].…”

Influence of particle morphology on catalytic performance of CeO₂/ZrO₂ for soot oxidation

“…In order to gain information on the activation of oxygen species and its participation in soot oxidation, isotopic transient kinetic analysis was made on CeO 2 /ZrO 2 , where the isotopic product (C 16 18 O 2 /He in the reaction stream were measured by a quadrupole mass spectrometer at 450°C. Figure 5 shows the product responses obtained for CeO 2 Haneda et al: Influence of particle morphology on catalytic performance of CeO 2 /ZrO 2 for soot oxidation directly participate in soot oxidation and the lattice oxygen in CeO 2 /ZrO 2 is reactive species.…”

“…In contrast with the product responses obtained for CZ(IMP), on the other hand, the formation of C 16 O 2 on CZ(CP) was relatively slow, and its amount was slowly decreased with time on stream. In addition, the formation of trace amount of C 16 …”

“…According to the isotopic product responses obtained for CZ(IMP) and CZ(DP) [Figs. 4(a) and 4(c)], a quick decrease in the amount of C 16 O 2 was clearly observed, suggesting that the lattice oxygen in the bulk of CeO 2 particles cannot directly participate in soot oxidation. In addition, the finding that the amount of C 16 O 18 O was gradually increased with time on stream suggests that the oxygen species created via the migration of adsorbed oxygen species into the subsurface of CeO 2 particles is highly reactive for soot oxidation.…”

Synthesis and characterization of ceria nanomaterials.

“…However, it has been a very difficult task for most of the practical catalysts (Kung, 2003). In general, high-surface area nanocatalytic materials exhibiting numerous crystal faces, edges, and corners, which are conventionally considered active sites for the adsorption of reactants (Terribile, 1997;Daturi, 2000 andStoimenov, 2003), should generate better catalytic performance.…”