THE MOO3-AL2O3 INTERACTION - INFLUENCE OF PHOSPHORUS ON MOO3 IMPREGNATION AND REACTIVITY IN THIOPHENE HDS

Two series of catalysts, Mo/A1203 and 1 wt% P-Mo/Al203, containing between 0 and 4.7 wt% MoO3 have been investigated by FT-IR spectroscopy of the v(OH) region. It is seen that molybdena reacts preferentially with surface P-OH groups, and also that the A1-OH groups are more reactive towards these loadings of molybdena in the presence of phosphorus. This is interpreted as resulting in an increase in Mo dispersion for the P-Mo/Al203 catalysts. Sulphiding/reduction of the catalysts results in regeneration of few surface hydroxyls for the Mo/Al203 catalysts, but many are regenerated for the P-Mo/Al203 catalysts. This indicates that molybdena on P/Al203 is more easily sulphided/reduced than on γ-Al203; in particular, molybdena bonded to P-OH groups is readily sulphided. These factors may explain the improved thiophene HDS activities of the P-Mo/Al2O3 catalysts. © 1992.