On the interaction of carbon monoxide with ternary Cu/ZnO/Al2O3catalysts: modeling of dynamic morphological changes and the influence on elementary step kinetics

Abstract

This paper focuses on gas-phase induced dynamic morphological changes of the catalyst, in particular by carbon monoxide. Those structural changes are studied in terms of hydrogen temperature-programmed desorption (TPD) from carbon monoxide pre-treated surfaces. Modeling the hydrogen TPD from the pre-treated catalyst shows activation of Cu(110) and Cu(100) planes. This is in good agreement with previously shown morphological changes in different gas atmospheres observed from in situ EXAFS and TEM measurements and observed transient maxima of methanol synthesis upon CO pre-treatment which has been reported in the literature. The obtained hydrogen desorption energies for the respective copper surfaces are physically reasonable. This surface heterogeneity is further implemented in a microkinetic model to describe the temperature-programmed surface reaction (TPSR) between carbon monoxide and adsorbed oxygen. It is found that a logarithmic coverage-dependence on adsorbed oxygen is essential for obtaining good agreement between simulation and experiment. For high oxygen loadings the apparent activation energy is essentially constant, which is in good agreement with literature results.