Spectroscopic evidence for Rh-CO-Zr sup 4+ surface species formed on Rh/ZrO sub 2 catalyst

Journal Article · Wed Nov 01 00:00:00 EST 1989 · Journal of Catalysis; (USA)

DOI:https://doi.org/10.1016/0021-9517(89)90268-6· OSTI ID:7089920

Guglielminotti, E ^[1]

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1. Universita di Torino (Italy)

Rh/ZrO{sub 2} prepared from Rh carbonyls contains highly dispersed Rh crystallites and is interesting as a catalyst for syngas conversion to C{sub 2}-oxygenated molecules. In particular, the selectivity to ethanol seems to be increased for Rh supported or promoted by metal oxides showing both acid and basic properties, such as TiO{sub 2}, ZrO{sub 2}, and V{sub 2}O{sub 3}. Notwithstanding the different and partially conflicting hypotheses on the mechanism of formation of ethanol and other oxygenated molecules, there is not doubt that the promoter effect of the support influences the temperature of CO dissociation: this temperature is lowered from 483 K for Rh/SiO{sub 2} to 448 K for Zr{sup 4+}-promoted Rh-Zr (1:1)/SiO{sub 2} catalyst. Similar results are obtained for Rh/SiO{sub 2} promoted by oxidic phases of Ti, V, and Mn located at the surface of Rh particles. Evidence for this effect is given by the IR spectra of CO adsorbed on these systems at room temperature (RT) after reduction at 673 K. These spectra show the usual linear and bridged CO species on Rh{sup 0} at 2040-2060 and 1880 cm{sup {minus}1}, respectively, accompanied by a broad and not well resolved shoulder between 1750 and 1520 cm{sup {minus}1} (1670 cm{sup {minus}1} for the Zr-promoted catalyst). These low-frequency CO bands have been assigned, in accord with the spectral position of analogous homogeneous species, to a tilted CO group, C-bonded to Rh{sup 0} and O-bonded to the promoter metal ion. The formation of this surface species evidently favors the CO dissociation process. To ascertain if a similar species is formed on a Rh/ArO{sub 2} system, the author has carried out an accurate Fourier transform-infrared (FT-IR) spectroscopic investigation.

• OSTI ID: 7089920
• Journal Information: Journal of Catalysis; (USA), Vol. 120:1; ISSN 0021-9517
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
10 SYNTHETIC FUELS
CARBON MONOXIDE
DISSOCIATION
ETHANOL
SYNTHESIS
RHODIUM
CATALYTIC EFFECTS
ZIRCONIUM OXIDES
CARBONYLS
CATALYST SUPPORTS
CHEMICAL COMPOSITION
CHEMICAL PREPARATION
FOURIER TRANSFORMATION
HYDROGEN
HYDROGENATION
INFRARED SPECTRA
PROMOTERS
SURFACE AREA
SURFACE PROPERTIES
SYNTHESIS GAS
ALCOHOLS
CARBON COMPOUNDS
CARBON OXIDES
CHALCOGENIDES
CHEMICAL REACTIONS
ELEMENTS
FLUIDS
GASES
HYDROXY COMPOUNDS
INTEGRAL TRANSFORMATIONS
METALS
NONMETALS
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PLATINUM METALS
SPECTRA
TRANSFORMATIONS
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
ZIRCONIUM COMPOUNDS
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100200 - Synthetic Fuels- Production- (1990-)