Monolithic catalysts — non-uniform active phase distribution by impregnation Original Research Article

During preparation of monolithic catalysts via impregnation of monolithic structures, an inhomogeneous active phase distribution can evolve on the scale of the whole monolithic structure. This is demonstrated by the Ni/Al2O3/cordierite system, investigated as a model system. Macroscopic redistribution of the active phase precursor occurred during drying of the monolithic structure after impregnation due to capillary suction, resulting in an accumulation of the active phase in an outer shell of the monolithic structure. Other solvent removal techniques like freeze-drying or microwave drying, or preparation techniques like deposition–precipitation can prevent this accumulation by immobilization of the precursor phase, resulting in a uniform active phase distribution throughout the monolithic catalyst.