A STUDY ON THE PREPARATION OF SUPPORTED METAL-OXIDE CATALYSTS USING JRC-REFERENCE CATALYSTS - I - PREPARATION OF A MOLYBDENA-ALUMINA CATALYST - PART 2 - VOLUME OF AN IMPREGNATION SOLUTION

Ten types of 13 wt% MoO3/Al2O3 catalysts were prepared by a convention al impregnation or equilibrium adsorption method using a common extrud ate support. These catalysts were subjected to a comprehensive charact erization and catalytic reactions to find important preparation parame ters in practical preparations. It was demonstrated in the present gro up study that the formation of crystalline MoO3 was strongly correlate d with the Mo segregation on the outer surface of the extrudate. When the amount of the impregnation solution was large (ca. 10 cm(3) g-Al2O 3-1), a considerably homogeneous distribution and high dispersion of M o oxide species were attained irrespective of the other preparation pa rameters. It is suggested that when a pore volume impregnation or inci pient wetness technique is employed, drying processes strongly affect the dispersion and distribution of Mo oxide species. Drying at a reduc ed pressure is suggested to result in a segregation of Mo oxides on th e outer surface of the extrudate, and accordingly a formation of cryst alline MoO3. (C) 1998 Elsevier Science B.V. All rights reserved.