The effect of an Fe promoter on Cu/SiO2 catalysts for improving their catalytic activity and stability in the water-gas shift reaction

Abstract

In this study, the water-gas shift (WGS) reaction is investigated over Cu/SiO₂ catalysts with and without an iron promoter. By adding a small amount of iron, the catalytic activity and stability of Cu/SiO₂ are effectively improved. The oxidation of Cu/SiO₂ catalysts is considered to be the major factor for the deactivation of Cu catalysts. Fe oxides in Cu–Fe/SiO₂ catalysts surprisingly inhibit the oxidation of Cu and increase the catalytic stability of Cu–Fe/SiO₂ catalysts. The role of the Fe promoter in Cu/SiO₂ catalysts in the WGS is thoroughly investigated using a variety of experiments, such as H₂-temperature-programmed reduction (H₂-TPR), IR spectroscopy, temperature-programmed desorption (TPD) and in situ X-ray absorption spectroscopy (XAS). For the Cu–Fe/SiO₂ catalysts, both reactants, CO and H₂O, prefer to adsorb on the defect sites on the Cu surface and on Fe oxides, respectively. The higher performance and stability of the Cu–Fe/SiO₂ catalyst for the WGS reaction is explained based on the rapid dissociation of H₂O on the Fe promoter.