Equilibrium adsorption of molybdenum on different carbon supports resulted in widely varying catalyst uptakes. The results were rationalized on the basis of varying degrees of electrostatic interaction between the catalyst precursor and the supports. This interaction is known to be dependent on the surface charge of the support (which in turn depends on the pH of the catalyst precursor solution) and the charge of the ionic precursor. The carbon supports were subjected to widely varying thermal and chemical pretreatments. Their surface charge (electrokinetic mobiIity as a function of pH) was determined by electrophoresis. This study and a critical analysis of the Iiterature illustrate the heretofore mostly neglected fact that, for achieving controlled catalyst uptake and/or a high degree of catalyst dispersion, it is not sufficient to create adsorption (or catalyst anchoring) sites on the carbon support surface; these must also be made accessible to the catalyst precursor. If the isoelectric point of the support is known, the precursor can be chosen and/or the solution pH can be modified to favor catalyst precursor/support interaction (e.g., adsorption), and thus maximize initial catalyst dispersion.
Key Wo~~~arbon-supported catalysts, adsorption, electrokinetic properties, surface charge.