08th February 2017, Wednesday, 04:00‐04:30 pm (25+5 mins), ChE Seminar hall
Development Of Crystallite Scale Model For Oxygen Spillover In A Three Way Catalyst
A crystallite scale model is developed to study the storage and regeneration of oxygen on automotive catalysts which contain ceria. The model is based on the surface diffusion of oxygen in ceria, and is able to predict the spill-over of oxygen between the Pt and ceria species. The coupling between the spill-over process and the reaction on the active metal crystallites is incorporated into the model. The crystallite scale model is coupled with the reactor-scale model which considers the physical processes of convection, diffusion and reaction. An elementary based kinetic approach is used to predict the oxidation of CO under the transient lean and rich conditions, typically encountered in a automotive catalyst. The reverse spillover of stored oxygen on ceria followed by its reaction with CO to form CO2 is predicted by the model. The model is able to predict the oxidation and reduction of ceria under the transient conditions. The variation of surface diffusivity with temperature and its effect on the catalyst activity is predicted by the model. The CO uptake on ceria-zirconia supported noble metals is predicted to be higher as compared to a ceria only support. The breakthrough time of CO in the exhaust under conditions of continuous feed of CO is found to increase with an increase in the surface diffusivity of oxygen. The model can be used to design future catalysts, which work on the principle of oxygen storage and release.