Influence of Vanadium or Cobalt Oxides on the CO Oxidation Behavior of Au/MO x/CeO 2-Al 2O 3 Systems

Abstract

A series of V 2O 5- and Co 3O 4-modified ceria/alumina supports and their corresponding gold catalysts were synthesized and their catalytic activities evaluated in the CO oxidation reaction. V 2O 5-doped solids demonstrated a poor capacity to abate CO, even lower than that of the original ceria/alumina support, owing to the formation of CeVO 4. XRD, Raman spectroscopy, and H 2-temperature programmed reduction studies confirmed the presence of this stoichiometric compound, in which cerium was present as Ce 3+ and its redox properties were avoided. Co 3O 4-doped supports showed a high activity in CO oxidation at subambient temperatures. The vanadium oxide-doped gold catalysts were not efficient because of gold particle agglomeration and CeVO 4 formation. However, the gold-cobalt oxide-ceria/alumina catalysts demonstrated a high capacity to abate CO at and below room temperature. Total conversion was achieved at -70°C. The calculated apparent activation energy values revealed a theoretical optimum loading of a half-monolayer.