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Catalysis Letters

, Volume 14, Issue 1, pp 57–64 | Cite as

Effect of lithium and residual nitrate species on platinum dispersion in Pt/Al2O3 catalysts

  • Fabio B. Passos
  • Martin Schmal
  • Roger Fréty
Article

Abstract

The effect of lithium (ex LiNO3) on the metallic dispersion of 0.8 wt% Pt/Al2O3 catalysts, prepared by different impregnation techniques, was investigated by temperature programmed reduction (TPR) and the frontal method of H2 chemisorption. The temperature at which platinum precursor is reduced at a maximum rate (543 K) was not modified by 0.1 wt% lithium addition, whatever the preparation technique used. The dispersion values of platinum (70–90%), after reduction at 773 K, were slightly dependent on the preparation procedure. After the addition of 0.8 wt% lithium the TPR profile presented two well defind peaks and the dispersion values (20–50%), measured after reduction at 773 K, presented a significant decrease. The results are linked with the presence of residual nitrate ions, that had not been eliminated during calcination at 773 K in air, but had been decomposed under the reducing atmosphere of the TPR experiment.

Keywords

Pt/Al2O3 Li NOx TPR metal dispersion hydrogen chemisorption H2-O2 titration 

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Copyright information

© J.C. Baltzer A.G. Scientific Publishing Company 1992

Authors and Affiliations

  • Fabio B. Passos
    • 1
  • Martin Schmal
    • 1
  • Roger Fréty
    • 2
  1. 1.COPPEUniversidade Federal do Rio de JaneiroBrasil
  2. 2.Institut de Recherches sur la CatalyseCNRSVilleurbanne CedexFrance

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