Temperature-programmed desorption and infrared study of CO and H2 adsorption on Cu/ZnO catalysts
1988; Elsevier BV; Volume: 110; Issue: 1 Linguagem: Inglês
10.1016/0021-9517(88)90302-8
ISSN1090-2694
Autores Tópico(s)Catalysts for Methane Reforming
ResumoWe have characterized a series of CuZnO catalysts prepared by several methods, using a combination of adsorbate uptake measurements, temperature-programmed desorption, and FTIR spectroscopy applied to CO, H2, and O2 adsorbates. Adsorbed CO is present on the reduced catalysts in several adsorption states which are distinguished by different vibrational frequencies in the range 2104-2067 cm−1, and which desorb with apparent activation energies in the range 10–16 kcal/mol. When CO is adsorbed on oxidized catalysts, the frequencies shift to 2136-2110 cm−1 and the highest desorption energy increases to 19 kcal/mol. For H2 adsorbed on reduced catalysts, a single desorption state which has an apparent activation energy of 20–21 kcal/mol is observed. When H2 is adsorbed on oxidized catalysts, the desorption energy of this state increases to 26–27 kcal/mol. For the reduced catalysts, the amounts of reversible CO and H2 adsorbed are found to correlate linearly with the amount of O2 chemisorption measured at 98 K, with relative uptakes for CO, H2, and O2 in the ratio 9:2:10. These results are interpreted to suggest that Cu is present as metallic clusters which expose a large fraction of high-index surface planes and that the chemical behavior of these planes is significantly different from that of low-index single crystal planes.
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