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XPS Studies of characterized Cu/Al 2 O 3 , Zn/Al 2 O 3 and CuZn/Al 2 O 3 , catalysts
Author(s) -
Moretti Giuliano
Publication year - 1991
Publication title -
surface and interface analysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.52
H-Index - 90
eISSN - 1096-9918
pISSN - 0142-2421
DOI - 10.1002/sia.740171009
Subject(s) - x ray photoelectron spectroscopy , spinel , calcination , copper , zinc , inorganic chemistry , solubility , catalysis , ion , hydrogen , chemistry , materials science , analytical chemistry (journal) , metallurgy , chemical engineering , engineering , chromatography , biochemistry , organic chemistry
By XPS it is confirmed that copper‐containing catalysts supported on alumina and calcined at high temperature (673–873 k for 24 h.), with or without zinc addition, have a ‘surface spinel’ structure. Combining the XPS results with previous results obtained by vis–UV reflectance spectroscopy and XRD we show that the limit of solubility of Zn and Cu ions in γ‐alumina, at a calcinations temperature of 873 k, about 20 and 10 wt.% (by weight), respectively. In the CuZn/Al 2 O 3 , catalysts prepared from Zn/Al 2 O 3 , a surface enrichment of copper occurs if the Zzinc ions are already presents in an amount larger than the surface solubility. The presence of zinc on the surface increases the reducibility under H 2 of the Cu(II) ions compared to the same ions in the pure copper surface spinel. This may be due to the role of Zn(II)O(II) aggregates in the activation of the hydrogen molecule and/or to the segregation of CuO species on the Zinc surface spinel.