Effect of lithium and residual nitrate species on platinum dispersion in Pt/Al2O3 catalysts |
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Authors: | Fabio B Passos Martin Schmal Roger Fréty |
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Affiliation: | (1) COPPE, Universidade Federal do Rio de Janeiro, Caixa Postal 68502, CEP 21941, Brasil;(2) Institut de Recherches sur la Catalyse, CNRS, 2, Av. Albert Einstein, 69626 Villeurbanne Cedex, France;(3) Present address: Departamento de Engenharia Quimica, Universidade Federal Fluminense, Rua Passos da Patria, 156, CEP 24210 Niteroi, Brasil |
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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. |
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Keywords: | Pt/Al2O3 Li NO
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TPR metal dispersion hydrogen chemisorption H2-O2 titration |
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