Design and Preparation of Impregnated Catalysts

Abstract Solid catalysts in common use are typically in the form of small metal crystallites dispersed on the internal surface of the porous support. Advantages of these supported-metal catalysts lie in their high surface-to-volume ratio and the high thermal stability endowed by the dispersion. Such catalysts are commonly produced by liquid-phase impregnation in which a dry or wet pellet of the porous support is impregnated with a solution of a compound of the desired catalytic constituent. During impregnation and subsequent drying, small crystallites of the catalyst precursors are deposited on the internal surface of the support material. The impregnation and drying steps involve mass and /or heat transfer processes which often do not reach equilibrium, resulting in nonuniform concentration profiles of impregnant, or "impregnation profiles" along the radius of the support pellet.