Through Control of Wetting and Drying Conditions of Monolithic Supports towards a Uniform Catalyst Distribution Gorazd Berčič* *Laboratory of Catalysis and Chemical Reaction Engineering, National Institute of Chemistry, Hajdrihova 19, 1001 Ljubljana, Slovenia. Fax: 00 386 14760 300; Tel: 00 386 14760 282; E-mail: gorazd.bercic@ki.si Abstract The paper presents an optimized wetting and drying procedure for a preparation of monolithic catalysts. The catalyst precursor consumption was minimized by applying tailored incipient wetness impregnation technique. The homogeneous distribution of the active phase within the monolithic catalysts was achieved by drying of the impregnated monoliths under a forced flow in a specially designed dryer. The dryer operated at ambient conditions with high recycle flow of drying gas. The direction of recycle flow was periodically alternated by a pneumatically driven valve assembly. The effect of the proposed impregnation method is demonstrated with an analysis of the Ni distribution in the impregnated Al 2 O 3 monolith supports. Key words: alternated recycle flow, monolith impregnation, monolith drying, nickel distribution INTRODUCTION Monolithic catalysts are used in almost all fields of heterogeneous catalysis. Due to their unique properties such as high void fraction, high surface area and consequently low pressure drop, they are used for gas phase processes where temperature changes are not crucial to process selectivity and conversion. At the beginning, monolithic catalysts were used as automotive catalytic converters, DeNOx catalysts or oxidation catalysts for the treatment of flue gasses from chemical plants [1-3] . Monolithic catalytic reactors also hold large potential in multiphase applications and they have already successfully replaced conventional slurry and trickle bed reactors [4,5] . When developing the process, many different catalysts have to be prepared and tested to find the optimal combination of elements for a particular process and desired operating conditions. Before depositing catalyst precursors on monoliths the latter are usually washcoated with slurries containing alumina, zirconia, titania or silica [1] in order to increase the surface area for catalyst deposition. Washcoats usually also contain promoters and stabilizers (for example, oxides of the following elements Ce, Zr, La, Mn, Mg, Ba, Fe, Ca, K etc) which increase the catalytic activity and selectivity and stabilise the structure of the catalyst [6,7] . Washcoats are required for nonporous supports while the washcoating of porous supports is arbitrary and depends on the support surface area [8] . For a uniform distribution of the active phase the most important steps are the application of the active phase to the monolith support and the drying of the support [9,10] . Only those methods applicable to the wet impregnation of porous ceramic monoliths are mentioned below. It is characteristic of the incipient wetness impregnation method that the volume of the impregnation solution containing the catalyst precursor Published in: Drying Technology (2015), 33, 72-82. 1