XPS STUDIES OF SUPPORTED TUNGSTEN CARBIDE(S)

The XPS of carburized Al2(WO4)3, 12% WO3, 28% WO3 and (3.9% Pt + 26% WO3) supported on gamma-Al2O3 has been reported. Argon ion bombardment or hydrogen at 1073K enabled to reduce more than 50% of the W(VI) to W(0) in apparent one single step process. Severe conditions of reduction by H-2 and carburization using CH4/H2 mixture were required in order to transform 90% of the W in Al2(WO4)3 to tungsten carbide. Lesser amount of WC were obtained in the case of supported systems due to a very strong metal-support interaction. Argon ion bombardment employed as reducing agent enabled to optimize the reduction conditions of these tungsten oxide systems. It has also been observed that WC could be reduced to the elemental W(0) upon Ar+ bombardment. Although indications about the presence of oxycarbide species have been observed, no conclusive evidence about its exact structure could be formulated.