MORPHOLOGY AND ACTIVITY OF MOS2 ON VARIOUS SUPPORTS - GENESIS OF THE ACTIVE PHASE

The morphology and hydrodesulfurization (of thiophene) activity of unpromoted MoS2 supported on alumina, silica, titania, and zirconia have been examined. In the oxidic catalyst, no surface molybdenum phases could be identified by transmission electron microscopy. For all supports except titania, an additional bulk molybdenum oxide phase appeared above a particular Mo loading. In the case of the alumina support, bulk Al2(MoO4)3 also appeared. In the sulfided catalysts, the bulk species retained their original morphology and were surrounded by a skin of MoS2 several layers thick. The core of the bulk MoO3 was reduced to Mo metal. On the surface of the SiO2 and Al2O3, the MoS2 was present as flakes up to five layers thick, sitting vertically on the support. For TiO2 and ZrO2 the MoS2 was present as "islands," which expanded with increased Mo loading, eventually encapsulating the support particles. The reactivity behavior also fell into two groups, corresponding to the two forms of MoS2 morphology. The specific activity of MoS2 supported on TiO2 and ZrO2 was higher than that for the case of Al2O3 and SiO2 supports. © 1990.