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

The differences in the amphoteric properties Of WO3 and Al2O3 were exploited and cobalt precursors were selectively mounted on the tungsten oxide phase of a 12% WO3/Al2O3 composite. 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 revealed that this composite-supported catalyst's properties were significantly different from cobalt supported on alumina. Cobalt crystallites as well as a CoAl2O4 type of surface species are formed on the Al2O3 support. The presence of WO3 as a second-phase oxide offers the possibility for a greater number of surface compounds to be formed on the composite. Specifically, cobalt-tungsten interaction species are formed. We provide evidence that strongly suggests the active catalytic center in the conversion of H2 and CO to methane is a (cobalt-tungsten) interaction species. These active centers. are present on CO/WO3, Co/12% WO3/Al2O3, and a commercial cobalt/tungsten oxide compound. A portion of the cobalt: in these active centers is not reduced to the metallic state. © 1992.