Evaluation of sol-gel methods for the synthesis of doped-ceria environmental catalysis systems. Part I: preparation of coatings

Sol-gel technology can be employed for the synthesis of multi-component nan ophase environmental catalysts with enhanced catalytic activity, controlled composition and tailor-made pore structure together with their simultaneou s deposition upon porous supports. The conditions for effective deposition of nano-phase doped-ceria systems onto cordierite honeycombs through sol-ge l routes were investigated. For the direct casting from the sol phase, the sol rheological characteristics were adjusted and optimized so that homogen eous smooth washcoats were obtained. In this way, integrated support-cataly st assemblies suitable for high-temperature gas-solid catalysis were prepar ed. To overcome the inherently low loading percentage achieved per impregna tion when depositing directly the sols, the synthesis of sol-gel powders an d their deposition from aqueous slurries, as well as hybrid deposition meth ods using sol-gel powders dispersed in sols were tested as alternatives. Th e hybrid sol/powder systems proved to be the most attractive by combining a n effective loading procedure with desirable and fine-tuned coating charact eristics. (C) 2001 Elsevier Science Ltd. All rights reserved.