PLATINUM CERIA CO OXIDATION CATALYSTS DERIVED FROM PT/CE CRYSTALLINE ALLOY PRECURSORS/

Pt/Ce alloys treated with O-2, N2O, or CO/H-2 yield Pt/ceria catalysts that are active for CO oxidation. The most active catalysts are produ ced by N2O treatment of Pt(3)C(e)7 at 720 K, which leads to the highes t dispersion of both the Pt and ceria phases. This reflects the smalle r exotherm, which occurs with N2O, apparently a critical requirement f or production of a highly active catalyst. The performance of these Pt 3Ce7-derived catalysts is comparable with that of the best, recently a nnounced, materials prepared by wet chemical techniques. In all cases, most of the active material is invisible to X-ray diffraction and the catalysts exhibit very low CO-titratable Pt area (<0.05 CO/Pt). Prere duction in H-2 at 570 K greatly enhances the reactivity of a given cat alyst. CO TPR shows that highest activity correlates with a reduction state at similar to 510 K, suggesting metal-promoted CO oxidation by t he ceria. It seems possible that this high activity is associated with ceria spillover onto Pt, the spillover being facilitated by atomic-le vel mixing of Pt and Ce in the alloy precursor. (C) 1996 Academic Pres s, Inc.