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

Abstract

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} formore » 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.« less

Authors:
 [1]
  1. Universita di Torino (Italy)
Publication Date:
OSTI Identifier:
7089920
Resource Type:
Journal Article
Journal Name:
Journal of Catalysis; (USA)
Additional Journal Information:
Journal Volume: 120:1; Journal ID: ISSN 0021-9517
Country of Publication:
United States
Language:
English
Subject:
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; 010408* - Coal, Lignite, & Peat- C1 Processes- (1987-); 100200 - Synthetic Fuels- Production- (1990-)

Citation Formats

Guglielminotti, E. Spectroscopic evidence for Rh-CO-Zr sup 4+ surface species formed on Rh/ZrO sub 2 catalyst. United States: N. p., 1989. Web. doi:10.1016/0021-9517(89)90268-6.
Guglielminotti, E. Spectroscopic evidence for Rh-CO-Zr sup 4+ surface species formed on Rh/ZrO sub 2 catalyst. United States. https://doi.org/10.1016/0021-9517(89)90268-6
Guglielminotti, E. Wed . "Spectroscopic evidence for Rh-CO-Zr sup 4+ surface species formed on Rh/ZrO sub 2 catalyst". United States. https://doi.org/10.1016/0021-9517(89)90268-6.
@article{osti_7089920,
title = {Spectroscopic evidence for Rh-CO-Zr sup 4+ surface species formed on Rh/ZrO sub 2 catalyst},
author = {Guglielminotti, E},
abstractNote = {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.},
doi = {10.1016/0021-9517(89)90268-6},
url = {https://www.osti.gov/biblio/7089920}, journal = {Journal of Catalysis; (USA)},
issn = {0021-9517},
number = ,
volume = 120:1,
place = {United States},
year = {1989},
month = {11}
}