THE EFFECT OF 2ND-PHASE OXIDES ON THE CATALYTIC PROPERTIES OF DISPERSED METALS - PALLADIUM SUPPORTED ON 12-PERCENT-WO3/AL2O3

Our earlier study J. Catal. 135, 200 (1992)] of the properties of dispersed cobalt on a 12% WO3/Al2O3 composite oxide is extended here to palladium. Temperature-programmed reduction (TPRd), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and catalyst performance testing using H2/CO methanation as a test reaction were used in this study. We find for this system, where surface compounds do not form, that the controlling factor in the performance of Pd//12% WO3/Al2O3 catalysts is the Pd loading in relation to the number of adsorption sites available on the second-phase oxide that can accommodate the Pd precursor. The intrinsic activity of Pd/Al2O3 is about one order of magnitude greater than that of Pd/WO3. The lower activity of the latter appears to be due to Pd-W interactions. © 1992.