Kinetics of hydrogen chemisorption on supported molybdenum disulphide

Abstract

Chemisorption of H2 on MoS2‐Al2O3 catalyst was studied at different temperatures and initial pressures. The results when analysed according to the Elovich equation revealed multiple kinetic stages. Assigning two sets of boundary conditions to the equation, a statistical procedure employing least square analysis has been applied for the evaluation of the Elovich parameters a and α and their temperature dependence has also been followed. A comparison is made with the parameters derived by the graphical method. The role of initial surface saturation q0 on the sequence of the multiple kinetic stages is discussed. Excepting for descriptive purposes, the kinetic stage connotation is not strictly followed. On the other hand, all the first straight line portions of the Elovich plots for a given initial pressure including the single stage plots have been grouped together and the corresponding a and α were calculated. The merits of deriving the apparent activation energies from the initial rates rather than from α are discussed.

Review of second-order models for adsorption systems

“…Ritchie found a good linear relationship between t and q ∞ /(q ∞ − q) for the results of Austin et al [41], Bansal et al [42], Deitz and Turner [44], and Samuel and Yeddanapalli [43]. In recent years, the Ritchie equation has also been applied to solution/solid adsorption systems, for example, the adsorption of cadmium ions onto bone char [37], and the adsorption of Cd(II) onto acid-treated jackfruit peel [45].…”

“…Several adsorption results were examined using the Ritchie equation [33]. In the early years, the Elovich equation was applied to describe gas and vapour adsorption systems, such as the adsorption of carbon monoxide during the oxidation of polyvinylidene chloride [41], the chemisorption of hydrogen onto graphon [42], the measuring of the kinetics of the chemisorption of H 2 onto a MoS 2 + Al 2 O 3 catalyst [43], and the adsorption of water vapour by Vycor fibre [44]. These systems did not fit the Elovich equation very well.…”