(731e) Single Droplet Combustion Modelling for Catalyst Synthesis with Flame Spray Pyrolysis

Single droplet combustion model has been shown to provide understanding of nanomaterial synthesis in flame spray pyrolysis and could be further explored for the rational design of catalysts. A single droplet combustion model has been developed based on mass, momentum and energy conservations, phase change thermodynamics and film theory. The model reveals the stage of initial rapid heating up and rapid vaporization, and the stage of decreasing vaporization and constant droplet temperature as the two stages describing droplet vaporization phenomenon inside the flame. Also, the droplet temperature profile and the mass boundary layer around the droplet indicated by the model could be indicative of the intrinsic precursor vaporization rate and the resistance to the release of precursor vapor to combustion zone, respectively. Therefore, a smaller droplet can be predicted to have a higher precursor vaporization rate due to its smaller boundary layer thickness, while a droplet of ethyl hexanoic acid (EHA)/toluene mixture containing more EHA concentration will most probably result in increased precursor vaporization due to EHA’s low specific heat capacity. Applying phase doppler interferometry measurements of EHA/toluene sprays as the initial conditions in the model, six synthesis conditions assessed form droplets experiencing similar droplet temperature profile, but the mass boundary layer thickness deviate beyond 15 mm above the initial droplet position in the flame. These results suggest that cerium ethyl hexanoate precursor does not decompose in droplet at the L2O3.5P2.5 (liquid flow, ml/min; gas flow, L/min; pressure bar) and L3O4.5P1.5 synthesis conditions for the slowest and fastest release of precursor, respectively, due its high decomposition temperature. Precursor release could control the rate of precursor reactions and particle formation resulting in different catalysts’ activity. The model will be studied at measured flame temperature for more accurate design of catalysts and the catalytic performance of the designed catalysts will be evaluated.