Kinetics of Deposition of the Mo−Oxo Species on the Surface of γ-Alumina

The kinetics of deposition (adsorption, surface reaction) of molybdenum−oxo species on the surface of γ-alumina was studied at various pH's, impregnation temperatures, solute concentrations, and ionic strengths. The kinetic study confirmed the findings of the thermodynamic study performed previously concerning the influence of the aforementioned parameters on the extent of the Mo(vi) deposition and the mechanism of that deposition as well. It was found that the decrease in pH and ionic strength and the increase in the impregnation temperature increase the time required in order for the surface of the support to be saturated by the molybdenum−oxo species. Moreover, the kinetic study suggested that, at low pH's where adsorption predominates, the polymeric oxo species are exclusively adsorbed in the first 20 min and the deposition proceeds through the adsorption of the monomeric oxo species. This is expected to be very useful in designing the preparation of the molybdenum-supported γ-alumina catalysts. The s...