Modelling of NOx adsorption over NOx adsorbers

Modelling of the phenomena involved during the adsorption of NOx on NOx trap catalysts has been developed in order to predict the quantity of stocked barium nitrate and the emissions of NO and NO2, as a function of time and temperature. The mechanism of the process is sounded onthe adsorption of gas...

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Published in:Chemical engineering science 2003-05, Vol.58 (9), p.1793-1803
Main Authors: LAURENT, F, POPE, C. J, MAHZOUL, H, DELFOSSE, L, GILOT, P
Format: Article
Language:English
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Summary:Modelling of the phenomena involved during the adsorption of NOx on NOx trap catalysts has been developed in order to predict the quantity of stocked barium nitrate and the emissions of NO and NO2, as a function of time and temperature. The mechanism of the process is sounded onthe adsorption of gas species (NO, NO2, O2) on platinum sites, equilibrium reaction between adsorbed species followed by the formation of Ba(N03)2. This formation of barium nitrate is limited by the thermal decomposition reaction which liberates NO in the gas phase. The kinetic constant of decomposition of barium nitrate was determined by temperature programmed thermogravimetry on pure Ba(NO3)2, using the method of Freeman and Carroll. Other kinetic constants bound to the mechanism were estimated by fitting the results of the model to experimental results. The mechanism was validated for various values of the molar fraction of O2, the molar fraction of NO and various values of the NO/NO2 ratio in the gas entering the reactor. It was also tested with differentcatalyst compositions (variation of the platinum and BaO concentrations). The importance of oxygen in the process as well as the promoting role of NO2 was clearly demonstrated. (Original abstract - amended)
ISSN:0009-2509
1873-4405
DOI:10.1016/S0009-2509(03)00014-9