Vincett M.E., Tsamopoulos J.A., Lund C.R.F.
A mathematical model for the steam gasification of carbon using group VIII transition metal catalysts has been developed. The reaction mechanism is assumed to involve the dissolution of carbon into the metal catalyst at the front half of the spherical particle followed by diffusion of carbon through the particle and finally reaction on the surface of the rear half of the particle. A material balance on the carbon within the catalyst is then written both for the steady-state and unsteady reaction. The steady-state model reproduces the experimentally observed dependence of the rate of reaction upon particle size as well as a change in the apparent activation energy of the reaction. The model suggests that the change in apparent activation energy occurs as the rate-determining step changes from diffusion of carbon through the particle (at low temperature) to surface reaction rate. The unsteady model can qualitatively and quantitatively show the experimentally observed deactivation of the catalyst, but it does not have complete predictive capability because there are too many unknown physical constants. © 1990.