Characterization of a potassium-promoted cobalt- molybdenum/alumina water-gas shift catalyst

Abstract

A series of potassium-promoted CoMo/Al₂O₃ has been investigated by means of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and temperature-programmed reduction (TPR). CoMoO₄ was found in the CoMo/Al₂O₃ catalyst by XRD and is destroyed by the presence of potassium. The reducibility of molybdenum is enhanced by potassium in the CoMoK/Al₂O₃ catalyst and is easier to reduce to Mo^IV during sulfidation. In the oxidic state catalyst cobalt is increased on the surface by the addition of potassium. After sulfidation this phenomena disappeared, the distribution of cobalt remains at a constant level and is unaffected by the potassium content. The addition of potassium leads to a monotonical decrease of the molybdenum dispersion with the impregnating amount of potassium in the oxidic state catalyst but is more complicated after sulfidation. Potassium is well dispersed on the surface in both the oxidic and sulfided state. The activity in the water-gas shift reaction was correlated with the potassium content of CoMoK/Al₂O₃.