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.