Modeling CO Oxidation on Silica-Supported Iron Oxide under Transient Conditions

The oxidn. of CO on silica-supported hematite (Fe2O3) was studied by the step-response method in a tubular fixed-bed reactor at temps. 270-350 Deg. The oxidn. process appeared to proceed in two stages. First, oxygen atoms adsorbed on the surface of hematite react with gas phase CO according to an Eley-Rideal mechanism. Once that adsorbed oxygen has been consumed to some extent, surface oxygen from the lattice of iron oxide is removed in a second stage involving CO adsorption and CO reactive desorption steps, thus generating surface oxygen vacancies. Further redn. of hematite proceeds by diffusion of subsurface oxygen into surface oxygen vacancies. On this basis, a kinetic model was developed, which quant. describes the transient behavior of the oxidn. process. The activation energies and pre-exponential factors of the rate consts. and characteristic subsurface oxygen diffusion time could be detd. [on SciFinder (R)]