ISSN:
0142-2421
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Physics
Notes:
Using SiO2, γ-Al2O3 as typical examples for acidic, amphoteric and basic oxides, the effect of the support nature on the behaviour of Rh was studied by temperature-programmed reduction, transmission electron microscopy and IR spectroscopy of adsorbed CO. Reduction is much easier on SiO2 than on Al2O3 and MgO. The highest metal dispersion is stabilized on Al2O3, while particle aggregation to particles with diameters of up to 6 nm occurs on SiO2, during severe reduction and on MgO even under mild reduction conditions. The mobility of RHo atoms and the nucleation rates seem to be larger on MgO than on the other supports. In the presence of CO, the very small particles are disrupted with formation of Rh+(CO)2 complexes at temperature below 300 K; at higher temperatures CO acts as a reducing agent and induces particle growth. It seems that particle disruption is favoured on the supports having the more acidic OH groups. Apart from the support nature, the nature of the precursor complex in solution and the solvent play a decisive role for the reducibility of rhodium.
Additional Material:
7 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/sia.740120403
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