In situ studies on the structure of copper oxide/zinc oxide catalysts

Citation
Mm. Gunter et al., In situ studies on the structure of copper oxide/zinc oxide catalysts, J SYNCHROTR, 8, 2001, pp. 619-621
Citations number
9
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Apllied Physucs/Condensed Matter/Materiales Science
Journal title
JOURNAL OF SYNCHROTRON RADIATION
ISSN journal
0909-0495 → ACNP
Volume
8
Year of publication
2001
Part
2
Pages
619 - 621
Database
ISI
SICI code
0909-0495(200103)8:<619:ISSOTS>2.0.ZU;2-9
Abstract
Cu/ZnO supported on alumina is a well-known catalyst for steam reforming of methanol. In this work it is attempted to assess the influence of elementa l composition on the resulting active copper phase. XAFS measurements of ca lcined precursors were carried out at the Cu K edge and the Zn K edge. Corr esponding RDF show that both copper oxide and zinc oxide exhibit considerab le deviations from a linear dependence of their structure on the compositio n coinciding with changes in phase composition of hydroxycarbonate precurso r. From time-resolved in situ experiments at the Cu K edge the degree of re duction can be monitored using a combination of factor analysis (PCA) and l east-squares XANES fitting with suitable reference spectra (e.g. Cu metal, Cu2O, and CuO). It is shown that Cu2O forms prior to Cu. The extent of redu ction to Cu exhibited a typical nucleation growth behavior with an enhanced reaction rate for more diluted samples. Adding oxygen to the feed gas lead s to the formation of mixed Cu2+ and Cu+ phases accompanied by a complete l oss of activity in methanol steam reforming. After switching back to steam reforming conditions the activity is regained.