TRANSIENT FTIR STUDIES OF MULTIPLICITIES, OSCILLATIONS, AND REACTION NONUNIFORMITIES DURING CO AND ETHYLENE OXIDATION ON SUPPORTED PT AND PD CATALYSTS

Transient infrared spectroscopy was used to study the dynamics of CO and Ethylene oxidation on a Pt/SiO//2 catalyst wafer. Temperature and concentration programming techniques, combined with Fourier Transform Infrared (FTIR) spectroscopy, are used to study the temperature and concentration dependence of adsorbed and gas phase species, and to locate regions of multiplicity, instability and oscillatory behavior. Selected area measurements reveal that regions of reaction rate non-uniformities develop during oscillatory behavior. Similar results were observed during ethylene oxidation. Oscillations were observed in a reactor with an external recycle which decreased significantly the temperature effects. The results of CO oxidation are explained via an elementary step kinetic model, including heat and mass transport effects, and a pseudo-inhomogeneous reactor model to simulate non-uniformities.