Characterization and catalytic performances of hydrotreatment catalysts prepared with silicium heteropolymolybdates: comparison with phosphorus dopedcatalysts

The CoMo-based catalysts were prepared by impregnation of a gamma -alumina with Si-based heteropolycompounds. solutions. The impregnating solution, th e dried and the calcined catalysts were characterized with various physical techniques. Based on these characterizations, a detailed description of th e evolution of these entities during the preparation, as wen as the nature of the surface oxomolybdate species of the oxidic precursor have been deduc ed. It is shown that the use of these Si-based heteropolycompounds allows i ncreasing the thiophene conversion by comparison with classical preparation . This is assigned to the absence of foreign counter-ions in the impregnati ng solutions and to the formation of a different surface oxomolybdate phase . Moreover, comparison with phosphorus doped catalysts prepared with phosph orus heteropolycompounds suggests that the main role of phosphorus in the H DS catalysts consists in an optimization of the preparation of the oxidic p recursor. (C) 2001 Elsevier Science BN. All rights reserved.