Effects of surface orientation of alumina supports on the catalytic functionality of molybdenum sulfide catalysts

Two kinds of gamma -Al2O3 powders with different surface orientation ratios were used as supports of MoS2 catalysts. After Mo was loaded on the gamma -Al2O3 catalyst, we characterized the microstructures of the catalysts by using transmission electron microscopy (TEM) and then evaluated the catalytic functionality, such as hydrogenation (HYD) and hydrodesulfurization (HDS), by using model test reactions. Our results showed that relatively large (3-5 nm) basal-bonding MoS2 clusters with single layers were formed on the plate-like (PL) alumina, whose surface orientation was mainly {1 1 0} planes. The PL alumina-supported catalyst exhibited HYD-oriented functionality. Stacked basal-bonding or highly dispersed MoS2 clusters were formed on the spherical (SP) alumina, whose surface orientation was mainly {1 1 1} and {1 0 0} planes. Compared to the PL alumina-supported catalyst, the SP alumina-supported catalyst exhibited higher HYD and HDS activities and higher HDS-oriented functionality. Our results on the effects of surface orientation of alumina supports on the microstructure of MoS2 clusters obtained for alumina powders were consistent with those previously obtained for alumina single crystal thin films. This consistency indicates that our results obtained by using model catalysts can be applied to the designing of industrial catalysts. Our results also show that the catalytic activity and selectivity of MoS2 catalysts depended on the microstructures of MoS2 clusters that were affected by the surface orientation of gamma -Al2O3.Thus, the surface properties of gamma -Al2O3 support are important factors in controlling the catalytic functionality of MoS2-based catalysts. Our results indicate that the microstructure of MoS2 clusters can be controlled by tailoring the surface orientation of alumina supports. (C) 2001 Elsevier Science B.V. All rights reserved.