Raman and IR studies of surface metal oxide species on oxide supports: Supported metal oxide catalysts

Surface composition analysis by low-energy ion scattering

Temperature-programmed isotopic exchange of 18O2 with 16O of several oxides was carried out in the 200−900 °C temperature range. The oxides can be ranked according to their maximal rates of exchange obtained at the following temperatures:  CeO2, 410 °C ≫ CeO2-Al2O3, 480 °C ≈ MgO, 490 °C > ZrO2, 530 °C ≫ γ-Al2O3, 620 °C ≫ SiO2, 850 °C. Except on CeO2 and on CeO2-Al2O3 a simple exchange yielding initially 18O16O can be observed. With ceria containing oxides, the reaction occurs in part via a multiple exchange mechanism yielding initially 16O2 which is indicative of the presence of binuclear species (O2, O2-, or O22-) at the ceria surface. Chlorine-free rhodium catalysts supported on these oxides were prepared with metal dispersions between 32 and 89%. The presence of rhodium accelerates considerably the oxygen exchange with the support:  the maximal rates of the exchange can be observed at much lower temperatures, by about 200−300 °C with respect to the bare oxides. This is attributed to a spillover of oxyg...

Mobility of Surface Species on Oxides. 1. Isotopic Exchange of 18O2 with 16O of SiO2, Al2O3, ZrO2, MgO, CeO2, and CeO2-Al2O3. Activation by Noble Metals. Correlation with Oxide Basicity†

https://www.lehigh.edu/operando/Publications/2008%20New%20Insights%20W-ZrO2.pdf

New insights into the nature of the acidic catalytic active sites present in ZrO2-supported tungsten oxide catalysts

Surface Complexation Modeling and FTIR Study of Carbonate Adsorption to Goethite.

The adsorption of metal oxyanions on alumina

The effect of the isoelectric point on the adsorption of molybdates on fluoride-modified aluminas

Chemisorption of CO2 on Alumina-Supported Catalysts

Absolute surface coverages (θ) of a series of tungsten-alumina catalysts prepared by the equilibrium adsorption method were determined by ion scattering spectroscopy (ISS) and low-temperature CO adsorption. The θCO values for the W catalysts were very similar to those obtained with the ISS method, for a given W loading. A linear increase in W coverage with increasing W loading, reaching ~55% coverage for the 13.1% W solid, was observed. The calculated W cross-sections (22.0- 24.5A2/W) were in agreement with other reports in the literature. Due to the inherent limitations of each method, the combined use of ISS and low-temperature CO adsorption is recommended for estimating absolute surface coverages in tungsten-alumina catalysts.

F. M. Mulcahy

Papers

The adsorption of metal oxyanions on alumina

The effect of the isoelectric point on the adsorption of molybdates on fluoride-modified aluminas

Chemisorption of CO2 on Alumina-Supported Catalysts

Absolute surface coverage of tungsten^alumina catalysts

Effect of F and Mg on the Dispersion of Mo/Al2O3 and W/Al2O3