Catalytic behavior and active sites structure of PtAu/Al2O3 bimetallic catalysts prepared by surface redox reactions

Alumina supported Pt-Au bimetallic catalysts, in which Au was deposited ont o Pt by reduction of AuCL4- with adsorbed hydrogen, were studied using hydr ogen TPD and X-ray diffraction. Their catalytic behavior was tested in meth ylcyclopentane reaction. The gold inhibits the hydrogen adsorption indicati ng that gold atoms are deposited on platinum sites. In methylcyclopentane r eaction, the catalysts containing the largest amounts of Au, promoted the f ormation of dehydrogenation products although in conversions very low. Howe ver, the environmental conditions or oxidation treatments irreversibly affe ct the catalytic behavior in these systems, suggesting a rearrangement of t he metallic sites created by the redox reaction. This rearrangement effect was investigated by X-ray diffraction and by high resolution electron micro scopy (HREM) studies. (C) 2000 Elsevier Science B.V. All rights reserved.