An attempt at modelling the activity of Pt-Rh/Al2O3 three-way catalysts inthe CO plus NO reaction

This study deals with the kinetic behaviour of a Pt-Rh/Al2O3 three-way cata lyst (TWC) in the CO + NO reaction close to the actual conditions. Practica lly, it consists in validating a previous rate equation, established at 300 degreesC from a selected mechanism [P. Granger. J.J. Lecomte. L. Leclercq, G. Leclercq, J. Catal. 175 (1998) 194], in a wider range of temperature pa rticularly near 100% NO conversion. Preliminary calculations using a non li near least square method lead to an estimation of pre-exponential factors ( for k, the rate constant of the rate limiting step and for lambda (CO) and lambda (NO), the adsorption equilibrium constants of CO and NO). the activa tion energy for the dissociation of adsorbed NO molecules. and the enthalpi es of CO and NO adsorption (DeltaH(ads.CO) and DeltaH(ads.NO)) Thr temperat ure-programmed conversion and selectivity curves obtained in differential c onditions using a recycle fixed bed flow reactor have been modelled using t hese adjusted parameters. Based on CO chemisorption observations it was fou nd that a better fit is obtained by accounting for the coverage dependency of DeltaH(ads.co) and DeltaH(ads.NO). Finally, we have attempted to quantif y such effects. (C) 2001 Elsevier science B.V. All rights reserved.