Zirconia as a support for catalysts

Mercera, P.D.L.; Ommen, J.G. van; Doesburg, E.B.M.; Burggraaf, A.J.; Ross, J.R.H.

doi:10.1016/s0166-9834(00)80728-9

Cited by 340 publications

(118 citation statements)

References 45 publications

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“…The structure of the ZrO 2 support in the 1 wt % MoO 3 / ZrO 2 sample also changed with increasing temperature and tetragonal ZrO 2 was detected after treatment at 673 K for 1 h by its Raman bands at 152, 267, 316, 470, 608, and 644 cm -1 . 59 Tetragonal ZrO 2 was stable up to 873 K. Monoclinic ZrO 2 bands at 180, 192, and 382 cm -1 appeared after treatment at 973 K and higher temperatures. 60 Mo surface densities approach polymolybdate monolayer values (∼5 Mo/nm 2 ) for 11 wt % MoO x /ZrO 2 samples after treatment at temperatures above 723 K (Figure 1).…”

Section: Resultsmentioning

confidence: 89%

Structural Characterization of Molybdenum Oxide Supported on Zirconia

et al. 2000

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X-ray diffraction and X-ray absorption and Raman spectroscopies were used to determine the structure of dispersed and crystalline structures in MoO x /ZrO 2 catalysts useful in the oxidative dehydrogenation of alkanes. The MoO x surface density on ZrO 2 was varied over a wide range (0.35-50 Mo/nm 2 ) by changing the Mo content (1-44 wt % MoO 3 ) and the treatment temperature (393-973 K). Raman spectra showed that MoO x / ZrO 2 samples with low surface density (<5 Mo/nm 2 ) treated at temperatures below 873 K initially contain isolated tetrahedral MoO x species; these species oligomerize to form two-dimensional structures with bridging MosOsMo bonds as the surface density increased to values typical for a polymolybdate monolayer (∼5 Mo/nm 2 ). An increase in surface density led to a shift in the ν(ModO) Raman band to higher frequencies and to changes in the near-edge X-ray absorption spectra. Both of these are consistent with the growth of these polymolybdate domains with increasing Mo surface density, as also suggested by the concurrent decrease in the UV-visible absorption energy. Thermal treatment at 973 K led to the dissociation of MosOsMo bonds and to the formation of tetragonal-pyramidal OdMoO 4 species. For MoO x /ZrO 2 samples with Mo surface densities greater than 5 Mo/nm 2 , MoO 3 and Zr(MoO 4 ) 2 were detected by Raman and for larger crystallites also by X-ray diffraction. Treatment of these samples in air at 723 K led to the predominant formation of MoO 3 , while higher temperatures led to a solid-state reaction between MoO 3 and ZrO 2 to form Zr(MoO 4 ) 2 . This structural evolution was confirmed by the evolution of pre-edge and near edge features in the X-ray absorption spectra of these high surface density samples. Zr(MoO 4 ) 2 contains Mo 6+ cations in a distorted tetrahedral coordination with one oxygen bonded only to molybdenum and the other three shared by Zr and Mo atoms. The Raman bands observed for Zr(MoO 4 ) 2 at 750, 945, and 1003 cm -1 were assigned to ν sym (OsMosO), ν asym (OsMosO), and ν(ModO) vibrational modes, respectively, based on the analysis of the Raman bands observed after 18 O 2 exchange with lattice oxygen atoms. Bridging O atoms in MosOs Mo species exchanged with gas phase 18 O 2 more readily than terminal ModO species.

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Section: Resultsmentioning

confidence: 89%

Structural Characterization of Molybdenum Oxide Supported on Zirconia

et al. 2000

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“…4 ZrO 2 films are used for the production of fuel gas sensors, 5 fuel cells, 6,7 and in catalytic applications as supports or active phases. [8][9][10] The excellent biocompatibility makes also zirconia a material of choice for orthopaedic prosthesis and dental restorative applications. [11][12][13][14] The above mentioned properties are typical of the tetragonal and cubic high-temperature phases: 1,12 this has stimulated a considerable effort in the characterization of the conditions determining zirconia phase stability and transition.…”

Section: Introductionmentioning

confidence: 99%

Cluster-assembled cubic zirconia films with tunable and stable nanoscale morphology against thermal annealing

Borghi

Sogne

Lenardi

et al. 2016

Journal of Applied Physics

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Nanostructured zirconium dioxide (zirconia) films are very promising for catalysis and biotechnological applications: a precise control of the interfacial properties of the material at different length scales and, in particular, at the nanoscale, is therefore necessary. Here, we present the characterization of cluster-assembled zirconia films produced by supersonic cluster beam deposition possessing cubic structure at room temperature and controlled nanoscale morphology. We characterized the effect of thermal annealing in reducing and oxidizing conditions on the crystalline structure, grain dimensions, and topography. We highlight the mechanisms of film growth and phase transitions, which determine the observed interfacial morphological properties and their resilience against thermal treatments. Published by AIP Publishing. [http://dx

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“…[20] Zirconia is of particular interest as a result of its large field of applications ranging from catalysis to ceramics. [20,21] It exhibits desirable properties such as tuneable surface acidity/basicity (controlled by the addition of different dopants), redox properties, and tuneable porosity and surface area. In particular, sulfated zirconia [22] has been the object of extensive research, both applied and fundamental, owing to its characteristics: it causes not only modifications of the acid properties but also affects surface features (sulfates retard crystallization, stabilize the tetragonal phase, and improve the surface area and pore size).…”

Section: Introductionmentioning

confidence: 99%

Highly Dispersed Gold on Zirconia: Characterization and Activity in Low‐Temperature Water Gas Shift Tests

et al. 2008

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Gold-loaded zirconia and sulfated zirconia catalysts were tested in the low-temperature water gas shift reaction. The samples were characterized by N2 adsorption analysis, temperature-programmed reduction, X-ray diffraction, pulse-flow CO chemisorption, FTIR spectroscopy, and high-resolution transmission electron microscopy. A reference catalyst, Au/TiO2, provided by the World Gold Council was investigated for comparison. CO chemisorption and FTIR data indicate the presence of only highly dispersed gold clusters on the sulfated sample and both small clusters and small particles on the non-sulfated sample. Both gold-zirconia catalysts are much more active than the Au/TiO2 reference sample over all the temperature range investigated. The sample prepared on sulfated zirconia exhibits higher stability than the catalyst on unmodified zirconia. The prominent role in the water gas shift reaction of gold clusters in close contact with the support was deduced.

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Zirconia as a support for catalysts

Cited by 340 publications

References 45 publications

Structural Characterization of Molybdenum Oxide Supported on Zirconia

Structural Characterization of Molybdenum Oxide Supported on Zirconia

Cluster-assembled cubic zirconia films with tunable and stable nanoscale morphology against thermal annealing

Highly Dispersed Gold on Zirconia: Characterization and Activity in Low‐Temperature Water Gas Shift Tests

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