Raman spectroscopic investigation of the effect of H/sub 2/O and NiO on the surface structure of NiO-MoO/sub 3//Al/sub 2/O/sub 3/

Raman spectroscopic and ion scattering spectrometry (ISS) data is presented on (0-7)% NiO-15% MoO/sub 3//Al/sub 2/O/sub 3/ and (0-4)% NiO-7.5% MoO/sub 3//Al/sub 2/O/sub 3/. Both sets of catalysts were prepared with a Harshaw Al-4104 α-Al/sub 2/O/sub 3/. The surface areas of the support and the catalysts were approximately 200 m/sup 2//g. Molecular speciation of the two sets of catalysts were analyzed as a function of in-situ O/sub 2/ calcination and H/sub 2/O exposure by Raman spectroscopy and ISS. The incorporation of nickel into MoO/sub 3//Al/sub 2/O/sub 3/ is shown to perturb the spectral characteristics of the Raman active Mo = O stretching vibration. Such perturbations are discussed in relation to the structural characteristics of the catalysts. In addition, the effect of nickel on these structural properties is shown by in-situ Raman and ISS techniques to be different than the effect of H/sub 2/O. These differences are used to discuss interaction mechanisms and/or sites of interaction of Ni and H/sub 2/O with the molybdenum-oxygen units. Consequences of the molecular speciation on these oxide catalysts with relation to sulfidation and catalytic activity are discussed