IR-spectral study of the metal state in low-percentage alumina-rhenium and alumina-technethillm catalysts following high-temperature reductive treatment

Autor: A. P. Barkova, T. S. Dorokhina, O. V. Bragin, D. B. Furman, V. Yu. Borovkov, V. B. Kazanskii, A. V. Zaitsev
Rok vydání: 1993
Předmět:
Zdroj: Russian Chemical Bulletin. 42:624-627
ISSN: 1573-9171
1066-5285
DOI: 10.1007/bf00703992
Popis: The state of Re and Tc in low-percentage alumina-rhenium (0.25 % Re) and aluminatechnetium (0.1 % Tc) catalysts reduced by H2 at 500–900 °C was studied using IR spectra of the diffuse reflection of the adsorbed CO. A highly dispersed (probably two-dimensional) metal phase with a lowered electron-donating ability due to strong metal—support interaction is present on the surface of these catalysts along with the ionic forms of Re and Tc at +1 and +4 oxidation states. CO adsorbed on such metals in a linear form can be removed by evacuation even at ∼20°C. The amount of highly dispersed metal phase on the support surface increases monotonically with an increase in the activation temperature of Re/Al2O3 and Tc/Al2O3. The activity of the catalysts in the dehydrogenation ofn-dodecane varies directly with the concentration of the electron-deficient highly dispersed metal phase. It is therefore concluded that highly dispersed Re0 and Tc0 formed during high-temperature treatment by H2 are the precursors of the catalytically active centers in the paraffin dehydrogenation reaction.
Databáze: OpenAIRE
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