A microscopic model for catalyst surfaces. ii. supported catalysts. Technical summary report

A new 'pebbly surface' model of supported metal catalysts is presented which can explain observed multiplicity and oscillatory behaviour of catalyst particles. This model combines the dynamic behaviour of the individual metal crystallites on the surface of the support with diffusion and heat transfer processes in the porous particle. The bifurcation of oscillations is analyzed in terms of relaxation oscillations as well as by Hopf's theorem and it is shown how the bifurcation phenomena depend on the system parameters. The parameter study may be used to suggest operating conditions and catalyst design parameters such that sintering effects may be reduced. Qualitative comparisons with data for carbon monoxide oxidation at various temperatures show very good agreement; however, this present simple form of the pebbly surface model seems unable to predict the long period oscillations observed in hydrogen oxidation.