The Mo-Co-Al 2 O 3 System. II) Model of Adsorption of Molybdenum on Al 2 O 3 and on Co-Al 2 O 3

Abstract

A model which interprets the equilibrium adsorption of molybdenum on Al₂O₃ and on Co-Al₂O₃ is presented. This model assumes the adsorption of monomelic and polymeric species of molybdenum on two different adsorption sites of the support. It is proposed a) that the adsorption mechanism can be represented by two independent adsorption reactions; b) that each species is adsorbed only on one type of site, and c) that the adsorption isotherms can be represented by the sum of a Langmuir type expression for the monomer and a sigmoidal one for the polymer. By applying this model to the experimental isotherms obtained for the two systems under study (Mo/Al₂O₃ and Mo/Co-Al₂O₃), the equilibrium constants for adsorption on site 1 (K,) and on site 2 (K₂) and the numbers of adsorption sites S₁ and S₂ have been estimated. This adsorption model was confirmed by experimental results data and by spectroscopic studies.