Open AccessLow-Temperature IR Spectroscopy of CO Adsorption on Calcined Supported CeO2: Probing Adsorbed Species and Adsorbing Sites
Author(s) -
Gamal A. H. Mekhemer,
Mohamed I. Zaki
Publication year - 1997
Publication title -
adsorption science and technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.682
H-Index - 36
eISSN - 2048-4038
pISSN - 0263-6174
DOI - 10.1177/026361749701500506
Subject(s) - adsorption , chemistry , calcination , carbon monoxide , infrared spectroscopy , inorganic chemistry , in situ , lewis acids and bases , spectroscopy , oxygen , catalysis , organic chemistry , physics , quantum mechanics
Carbon monoxide adsorption on ceria dispersed on silica (CeSi) and alumina (CeAl) at 300–80 K was observed by in-situ IR spectroscopy. For control purposes, CO adsorption was also observed on unsupported CeO 2 and the individual support materials (SiO 2 and Al 2 O 3 ). The adsorbents were prepared ex situ by heating at 770 K (3 h) in air, and pretreated in situ by heating at 720 K (1 h) in oxygen and then in vacuum. The results, as disclosed by v(OH) (3900–3300 cm −1 ) and v(CO) (2250–2050 cm −1 ) spectra taken before and after CO adsorption, reveal that CO adsorbs on all of the test adsorbents at temperatures < 300 K only. The resulting adsorbed species include CO coordinated to Lewis acid sites (on all of the adsorbents, but not SiO 2 ), hydrogen-bonded CO (on all of the adsorbents, but not CeO 2 ) and CO bound to electron-rich defect sites (only on unsupported CeO 2 ). It is concluded that the dispersion of ceria, particularly on alumina, is associated with a considerable development of the Lewis acidity of Ce 4+ sites.