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 nanophase environmental catalysts with enhanced catalytic activity, controlled composition and tailor-made pore structure together with their simultaneous deposition upon porous supports. The conditions for effective deposition of nano-phase doped-ceria systems onto cordierite honeycombs through sol-gel routes were investigated. For the direct casting from the sol phase, the sol rheological characteristics were adjusted and optimized so that homogeneous smooth washcoats were obtained. In this way, integrated support-catalyst assemblies suitable for high-temperature gas-solid catalysis were prepared. To overcome the inherently low loading percentage achieved per impregnation when depositing directly the sols, the synthesis of sol-gel powders and their deposition from aqueous slurries, as well as hybrid deposition methods using sol-gel powders dispersed in sols were tested as alternatives. The hybrid sol/powder systems proved to be the most attractive by combining an effective loading procedure with desirable and fine-tuned coating characteristics. (C) 2001 Elsevier Science Ltd. All rights reserved.