The interaction of hydrogen with alumina-supported copper catalysts: A temperature-programmed adsorption/temperature-programmed desorption/isotopic exchange reaction study

The interaction of hydrogen with a series of copper catalysts (Cu/Al ₂O₃, Cu/ZnO, and Cu/ZnO/Al₂O₃) was studied by combining temperature-programmed (TP) techniques and the isotopic exchange reaction of H₂ and D₂ with microkinetic modeling. Various TP experiments (TP desorption, TP adsorption) were carried out, resulting in a set of kinetic parameters for a quantitative description. Only small differences in the kinetics of the ZnO-containing Cu catalysts and Cu/Al₂O₃ were observed, suggesting that the interaction of H₂ with the Cu surface is therefore only slightly influenced by the presence of zinc oxide, and alumina seems to act only as a structural promoter. Significant changes in the results were found when the treatment prior to the actual experiments was altered. From these observations and further supporting experiments it was deduced that a change in the morphology of the metallic Cu particles and surface alloying occur under more severe reducing conditions. These dynamical changes seem to be highly relevant for methanol synthesis.