In-situ EXAFS measurements have been made on the Cu/ZnO catalyst under reacting conditions at elevated as well as at ambient temperature. It was found that the local structure around the Cu atoms, which were believed to be the active atomic species, changes reversibly with heating/cooling cycles in a H2 stream. Between about 400 and 550 K highly dispersed Cu metal clusters appear, while metal clusters with metal-oxygen bonding exist below 400 K. Since this catalyst is used industrially around 550 K, the former should be regarded as the carrier of catalytic activity for the system. However, once this catalyst is heated above its active region, the Cu clusters coalesce into large crystalline particles and the change with heating/cooling cycles ceases to be reversible. This provides a rationale for a well-known loss of activity when this catalyst is operated at high temperatures. The results presented here emphasize the importance of characterizing catalysts under working conditions.
|Number of pages||6|
|Journal||Journal of physical chemistry|
|Publication status||Published - 1985 Dec 1|
ASJC Scopus subject areas
- Physical and Theoretical Chemistry