Comparison between different models for the catalytic oxidation of CO on a surface in the presence of non-desorbing impurities in the gas phase

Abstract

We apply kinetic Monte Carlo simulations to study the catalytic oxidation of CO on a surface in the presence of contaminants in the gas phase. The dynamic behavior of the process is simulated by models based on the Ziff-Gulari-Barshad model (ZGB). We analyze three ways in which the entrance mechanism of the oxygen atoms can be modified such that the unphysical oxygen poisoned phase that characterizes the ZGB model disappears. We study the behavior of these models in the presence of impurities in the gas phase. Once on the surface, the impurities cannot be desorbed and do not react. We calculate the phase diagrams of the three cases for different percentages of impurities and study the behavior of the CO₂ production. We found that the non-desorbing impurities have the effect of eliminating the discontinuous phase transition to a CO poisoned phase, and that in the steady state there is no production of CO₂. However in the transient phase there can be an important CO₂ production that depends on the model.