Bulk and Surface Structures of V2 O5 /ZrO2 Systems and Their Relevance for o -Xylene Oxidation
Zirconia-supported vanadium oxide systems, with V2O5 loadings ranging from V/Zr ) 0.033-0.270 atom ratios (0.2-2 monolayers), were prepared by impregnation of a porous ZrO2 substrate with ammonium metavanadate solutions. The surface structures of air-calcined samples were elucidated by Raman and X-r...
| Autores: | ; ; ; ; |
|---|---|
| Tipo de documento: | Artigo |
| Estado: | Published version |
| Data de publicação: | 2002 |
| País: | Argentina |
| Recursos: | Consejo Nacional de Investigaciones Científicas y Técnicas |
| Repositório: | CONICET Digital (CONICET) |
| Idioma: | Inglês |
| OAI Identifier: | oai:ri.conicet.gov.ar:11336/41530 |
| Acesso em linha: | http://hdl.handle.net/11336/41530 |
| Nível de acesso: | Acesso aberto |
| Palavra-chave: | https://purl.org/becyt/ford/2.7 https://purl.org/becyt/ford/2 |
| Resumo: | Zirconia-supported vanadium oxide systems, with V2O5 loadings ranging from V/Zr ) 0.033-0.270 atom ratios (0.2-2 monolayers), were prepared by impregnation of a porous ZrO2 substrate with ammonium metavanadate solutions. The surface structures of air-calcined samples were elucidated by Raman and X-ray photoelectron spectroscopic techniques and thermal desorption methods. Some insight into how the bulk structures of these materials developed upon thermal treatment was derived from the X-ray diffraction patterns and temperature-programmed reduction. At low V content, surface-dispersed vanadium oxide species were formed, which produced the transformation of the ZrO2 support from the tetragonal phase into the monoclinic one. At higher vanadium oxide contents, a solid-state reaction between V2O5 and ZrO2 occurred, with subsequent formation of the ZrV2O7 phase, this being the major V-containing phase. The reactivity of these surface structures was examined by looking at their performance for the oxidation of o-xylene to phthalic anhydride. Activity tests indicated that surface vanadium oxide species were more active for the oxidation of o-xylene but had a lower selectivity to phthalic anhydride. |
|---|