Microwave assisted syntheses of solvent-based colloidal sols of tailored ceria nanoparticles
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Microwave assisted syntheses of solvent-based colloidal sols of tailored ceria nanoparticles Poncelet O.1, Jouhannaud J.1, Chaumont D.2 1 CEA LITEN/DTNM/LCSN, 17 rue des Martyrs F-38054 Grenoble Cedex9, France 2 GERM, Institut Carnot de Bourgogne, UMR 5209 CNRS, Université de Bourgogne, 9 Avenue Alain Savary, B.P. 47870, 21078 Dijon Cedex, France ABSTRACT Crystalline nanoparticles of ceria (CeO2) were obtained in one pot synthesis in water using single-jet reactor or microwave assisted syntheses followed by a nanofiltration. These nanoparticles were dispersed with selective surface modifiers which allowed the self aggregation to be avoided when the polarity of solvent was tuned to non-polar medium. This was particularly true for ether acid modifiers. The exchange of solvent was directly performed in a nanofiltration unit leading to organic sols ready to use as fuel additives. INTRODUCTION The pressure of environmental laws in many advanced countries becoming more restricting year after year, automobile companies were asked for strongly control the vehicle carburant consumption which were distributed on the market as well as to eliminate toxic chemicals released from exhaust emission gases. This issue is particularly relevant to gasoline which is efficient in terms of carburant consumption but known to release toxic chemicals in exhaust gases. Among the materials able to solve these matters, ceria (CeO2) is a catalyst of choice due to the fact that it can work in two different ways [1,2]: first, as an oxygen storage device producing oxygen in the presence of reductive gases (CnHn and CO); secondly, by removing oxygen by interaction with oxidising species (NOx), resulting finally in exhaust gases composed of H2O, CO2 and N2. Extensive laboratory engine test data (thousands of hours) and on-road test data (millions of miles) conducted by Rhodia, Oxonica and Cerion Energy suggest that these gasoline additives are increasing fuel efficiency by 8 to 15% while reducing greenhouse gases by up to 15%, NOx by 8%, and gasoline particles matter by 30 to 40%. In order to be efficient ceria, has to be used under nanoparticular form directly added in the gasoline. The surface area developed by the nanoparticles due to their small size, enhance catalytic properties (both oxidation and reduction steps) kinetically, so the ignition delay time for nanosized particles in the combustion chamber of gasoline motors fits well with the high performance diesel motor characteristics. The true challenge is to be able to prepare stable solvent-based sols of crystalline ceria nanoparticles which could be used without plugging the injection nozzles. In this publication, we present two synthetic pathways forceria nanoparticles, single-jet reactor and microwave assisted processes, and their dispersion using selective surface modifiers. EXPERIMENT AND DISCUSSION The challenge was to set up new synthetic pathways allowing the production of ceria nanoparticles exhibiting the smallest size possible, since their efficiency as catalysts has
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