A STUDY ON THE PREPARATION OF SUPPORTED METAL-OXIDE CATALYSTS USING JRC-REFERENCE CATALYSTS - I - PREPARATION OF A MOLYBDENA-ALUMINA CATALYST - PART 3 - DRYING PROCESS

In the present part of the group study on the preparation of 13 wt% Mo O3/Al2O3, the effects of drying processes were investigated on the phy sicochemical and catalytic properties. Two series of catalysts were pr epared by a conventional impregnation technique and by an equilibrium adsorption method using a common extrudate support, XPS and EPMA resul ts demonstrated that the distribution of Mo oxide species in extrudate s was strongly affected by drying processes. A rapid drying, in partic ular at a reduced pressure, was found to induce a strong segregation o f Mo oxides on the outer surface of the extrudates, forming a sharp eg g shell type distribution of Mo. On the other hand, drying under stati c conditions produced a moderate egg shell type distribution, suggesti ng that a slow drying rate is favorable for a homogeneous distribution of Mo. The equilibrium adsorption technique was found to provide cons iderably flat Mo profiles inside the extrudates except for the utmost surfaces where Mo concentrations increased steeply. (C) 1998 Elsevier Science B.V. All rights reserved.