ISSN:
1572-879X
Keywords:
Lindlar catalyst
;
hydrogenation
;
Pd/CaCO3
;
Pd/Al2O3
;
Pd/SiO2 Pd/C
;
CO oxidation
;
Pd 3d binding energy
;
Madelung shift
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Abstract Various commercial supported palladium hydrogenation catalysts were studied by XPS and treated at ambient pressure with hydrogen and air. Unused catalysts exhibit a significant fraction of divalent Pd (oxide) which is reduced by hydrogen treatment at room temperature. Exposure to air in systems with carbonate, alumina, silica or active carbon as support causes the formation of a solid solution of oxygen in Pd characterized by a Pd 3d chemical shift of ca. + 0.4 eV. The absolute binding energy of Pd depends strongly on the matrix, indicating a significant contribution of extra-atomic screening, which prevents a direct comparison of reference samples and supported catalysts. Using the oxidation of CO to CO2 at 300 K as in situ chemical probe it was confirmed that Pd supported on carbonate, silica and alumina exists in the same metallic state which could be activated for the test reaction irrespective of the variation in XPS binding energies.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00765697
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