Infrared study of CO, CO2, H2 and H2O interactions on potassium-promoted reduced and oxidised silica-supported copper catalysts

Millar, Graeme J., Rochester, Colin H., & Waugh, Kenneth C. (1992) Infrared study of CO, CO2, H2 and H2O interactions on potassium-promoted reduced and oxidised silica-supported copper catalysts. Journal of the Chemical Society, Faraday Transactions, 88(10), pp. 1477-1488.

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Abstract

FTIR spectra are reported of CO, CO2, H2 and H2O on silica-supported potassium, copper and potassium-copper catalysts. Adsorption of CO on a potassium/silica catalyst resulted in the formation of complexed CO moieties. Whereas exposure of CO2 to the same catalyst produced bands ascribed to CO2 -, bidentate carbonate and complexed CO species.

Fully oxidised copper/silica surfaces gave bands due to CO on CuO and isolated Cu2+ cations on silica. Addition of potassium to this catalyst removed a peak attributed to CO adsorption on isolated Cu2+ cations and red-shifted the maximum ascribed to CO adsorbed on CuO.

For a reduced copper/silica catalyst bands due to adsorbed CO on both high and low index planes were red-shifted by 10 cm-1 in the presence of potassium, although the strength of the Cu - CO bond did not appear to be increased concomitantly. An explanation in terms of an electrostatic effect between potassium and adsorbed CO is forwarded. A small maximum at ca. 1510 cm-1 for the reduced catalyst increased substantially upon exposing CO to a reoxidised promoted catalyst. Correspondingly, CO2 adsorption allowed the identification of two distinct carboxylate species, one of which was located at an interfacial site between copper and potassium oxide.

Carboxylate species reacted with hydrogen at 295 K, on a reduced copper surface, to produce predominantly unidentate formate on potassium. In contrast no interaction was detected on a reoxidised copper catalyst at 295 K until a fraction of the copper surface was in a reduced state. Furthermore the interaction of polar water molecules with carboxylate species resulted in a perturbation of this structure which gave lower C----O stretching frequencies.

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ID Code: 61977
Item Type: Journal Article
Refereed: Yes
Keywords: infrared, catalyst, copper, potassium, methanol synthesis
DOI: 10.1039/FT9928801477
ISSN: 1364-5455
Subjects: Australian and New Zealand Standard Research Classification > CHEMICAL SCIENCE (030000) > PHYSICAL CHEMISTRY (INCL. STRUCTURAL) (030600) > Catalysis and Mechanisms of Reactions (030601)
Divisions: Current > Schools > School of Chemistry, Physics & Mechanical Engineering
Current > Institutes > Institute for Future Environments
Current > QUT Faculties and Divisions > Science & Engineering Faculty
Copyright Owner: Copyright 1992 Please consult the authors
Deposited On: 21 Aug 2013 23:29
Last Modified: 21 Aug 2013 23:29

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