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

Abstract

Kinetic expressions for slow (CH 4) and fast (C 3H 6) oxidizing hydrocarbons, a strongly adsorbed hydrocarbon (C 2H 2), 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.