The deposition of γ-Al2O3 layers on ceramic and metallic supports for the preparation of structured catalysts

Deposition of gamma -Al2O3 washcoats onto Aluminium and FeCrAlloy (R) supports in the form of slabs and onto alpha -Al2O3 tubes was performed according to a two-step procedure involving: (a) deposition of a bohemite primer, (b) deposition of the gamma -Al2O3 layer, both by dip coating into powder dispersions in HNO3 aqueous solutions. We present herein data concerning the effects of the major preparation variables (HNO3 and H2O concentrations in the dispersion, withdrawal velocity, drying temperature, number of dipping cycles, calcination temperature) on the deposited coating load and on the adherence of the washcoat. Based on a rheological characterisation of the gamma -Al2O3 dispersions, we propose also a correlation between their apparent viscosity and the washcoat load. Finally, we briefly illustrate the activity in catalytic combustion reactions of structured Pd-based catalysts prepared according to the investigated washcoating methods. (C) 2001 Elsevier Science B.V. All rights reserved.