Brigitte Martin

Three-way catalytic converter modelling: fast- and slow-oxidizing hydrocarbons, inhibiting species, and steam-reforming reaction

Kinetic expressions for slow (CH4) and fast (C3H6) oxidizing hydrocarbons, a strongly adsorbed hydrocarbon (C2H2), and the steam reforming reaction are proposed. They are based on the historical rate laws proposed by Voltz et al. (1973, Ind. Engng Chem. Proc. Res. Dev.12, 294–301) and Subramanian and Varma (1985, Ind. Engng Chem. Proc. Res. Dev.24. 512–516). The kinetic parameters are determined from the readily available laboratory light-off curves using a standard adiabatic model for the monolith. Comparisons of simulated results with engine experiments are successful and they show that: (1) light-off performance is much affected by a strongly adsorbed hydrocarbon even at the ppm level; (2) conversion under stabilized conditions depends on the slow-oxidizing hydrocarbons; (3) steam reforming is important under rich conditions. The proposed chemical description should allow assessing the effect of fuel composition and combustion characteristics on the efficiency of the converter.

From light-off curves to kinetic rate expressions for three-way catalysts

A new approach for obtaining reliable kinetic data from light-off curves is proposed. By fitting laboratory and simulated light-off curves with a simple 1-D model, apparent activation energies and frequency factors are adjusted using the Simplex method. The originality of the method is that kinetic parameters are obtained sequentially using simple mixtures. The whole set of parameters is then checked against experimental results involving all the reactants. Simulation results are satisfactory despite the empirical nature of the rate laws.