Surface spectroscopic characterization of cobalt-molybdenum-alumina catalysts

The structural characteristics of Co/Mo/Al/sub 2/O/sub 3/ hydrodesulfurization catalysts have been investigated with a variety of surface spectroscopic techniques: ESCA, ISS, and photoacoustic spectroscopy (PAS). All catalysts were prepared by sequential impregnation of Mo and Co into ..gamma..-Al/sub 2/O/sub 3/ with the Mo concentration held constant at 15% MoO/sub 3/ by weight as the cobalt concentration was varied from 1 to 9% CoO. In all catalysts interaction between Co and the support was observed which rendered a portion of the Co inert toward H/sub 2/ reduction and H/sub 2/S sulfidation. This interaction species (Co-t) is dominant for catalysts of low cobalt loading (i.e., 1% CoO). As the cobalt concentration is increased a new phase is formed characterized by interactions between Co and Mo. This species (Co-M) is produced up to a concentration of 7% CoO. Above this level, Co/sub 3/O/sub 4/ is formed. From ISS it was determined that the Co ions were situated beneath the Mo ions as Co-t and the Co-Mo interaction species. The presence of cobalt was found to have no effect on the reduction or sulfidation of Mo. 10 figures, 5 tables.