Process design of ultrasonic spray pyrolysis synthesis of RuO2/TiO2 nanoparticles for catalytic applications

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Industrial chlorine processes produce large amounts of by-product, much more than the market can absorb, resulting in a toxic-waste disposal problem. In current processes chlorine is recovered from HCl in oxidation processes, where titanium electrodes coated with a layer of mixed oxides of titanium, ruthenium and/or other noble metals are used. The main target of this study in the frame of the DFG-SPP Program is to develop novel process designs for RuO2/TiO2 nanocatalysts with advanced properties. The rutile structure shall be reached in one step from aerosol droplets of a precursor solu-tion using the ultrasonic spray pyrolysis USP. Because of more simple preparation and possible high effectivity nanoparticles of transition metal oxide such as CuO, CoO, NiO will be investigated as new alternatives. Instead TiO2 as catalyst carrier the synthesis of Al2O3 from aluminium nitrate and alumin-ium chloride will be performed. The average droplet size in an aerosol formed ultrasonically depends mostly on the solution properties (viscosity, surface tension, concentration, density, rheology) as well as the ultrasound frequency. For a better control of droplet morphology and final powder properties the investigated process will be especially designed with respect to the synthesis of nanosized particles. In contrast to conventional processes, the synthesis of nanostructured particles by USP is a com-pletely new approach that offers better control of droplet morphology and final powder. A correspond-ing theoretical model: one droplet to one nanoparticle shall allow for efficient prediction of nanoparticle distribution, such existing ideas will be improved considering different characteristics of precursor. Us-ing a laser diffraction measurement of produced aerosol will allow in situ prediction of the final nanoparticle size.