Infrared spectroscopic study of the adsorption and reactions of CO sub 2 on K-modified Rh/SiO sub 2

Journal Article · Thu Mar 01 04:00:00 EST 1990 · Journal of Catalysis; (USA)

DOI:https://doi.org/10.1016/0021-9517(90)90268-O· OSTI ID:6379394

Solymosi, F; Knoezinger, H ^[1]

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1. Universitaet Muenchen (West Germany)

Adsorption of CO{sub 2} on K-free Rh/SiO{sub 2} at 140 K produced only a strong band at 2,340 cm{sup {minus}1} characteristic of weakly bonded CO{sub 2}. There was no carbonate formation and CO{sub 2} desorbed completely from this surface below 250 K without any detectable dissociation. Co-adsorption of H{sub 2} + CO{sub 2} on Rh/SiO{sub 2} led to the formation of CO bands at 2,050 and 2,015 cm{sup {minus}1}, indicating the dissociation of CO{sub f2}. Formate bands were not observed. Adsorption of CO{sub 2} on K-modified Rh/SiO{sub 2} produced an intense band at 1,695-1,675 cm{sup {minus}1} and a weak band at 1,325-1,360 cm{sup {minus}1}, which are attributed to the formation of CO{sub 2}{sup {minus}} anions bonded to K{sup +} ions. Spectral changes observed above 200 K suggest that the species is transformed into bidentate carbonate characterized by absorption bands at 1,660, 1,525, and 1,360 cm{sup {minus}1}. As the same features were observed for Rh-free samples, it was concluded that both species are coordinated to K{sup +}-sites on the silica surface. CO{sub 2}{sup {minus}} reacted with hydrogen on (K + Rh)/SiO{sub 2} to give formate at temperatures as low as 150 K. No formate was produced on K/SiO{sub 2} in the absence of Rh.

• OSTI ID: 6379394
• Journal Information: Journal of Catalysis; (USA), Journal Name: Journal of Catalysis; (USA) Vol. 122:1; ISSN 0021-9517; ISSN JCTLA
• Country of Publication: United States
• Language: English

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ADSORPTION
ALKALI METALS
CARBON COMPOUNDS
CARBON DIOXIDE
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METALS
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OXIDES
OXYGEN COMPOUNDS
PLATINUM METALS
POTASSIUM
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SILICON OXIDES
SORPTION
SORPTIVE PROPERTIES
SPECTRA
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TEMPERATURE DEPENDENCE
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