Chemical Engineering Science, Vol.54, No.20, 4459-4468, 1999
CO oxidation in a fixed bed reactor with high frequency cycling of the feed
An experimental set-up is presented, which allows cycling of the feed for transient operation of fixed bed microreactors at frequencies up to 10 Hz. The set-up was applied for the transient oxidation of CO by O-2 over Pt/gamma-Al2O3,. The results gave clear evidence that CO may adsorb on oxygen covered sites under simultaneous production of CO2. O-2 does, however, not adsorb on CO covered sites, which causes a delay in the transient of the CO2 production. A kinetic model including rate parameters was presented, which gives an adequate description of the experimental data and provides much more detailed information than could be obtained from steady-state experiments. A simulation study is performed, with CO oxidation as an example, to explore how feed composition cycling is affected by diffusion inside catalyst pellets. If the time scale of diffusion inside the catalyst is much smaller than the time scale of the applied oscillation, intrinsic kinetics might be obtained from experiments with cycling of the feed. This statement supposes that diffusion limitation would be absent in the corresponding steady-state without composition cycling, and that the reaction kinetics is in the dynamic regime.