The Role of Intraparticle Diffusion in Kinetic Model Discrimination: Proof of Concept Testing for Methanol Dehydration

ABSTRACT The rate of a heterogeneous catalytic process may simultaneously be described by several rate equations. In this case, discrimination between the plausible kinetic models is required. An intrinsic kinetic model of a heterogeneous catalytic process may successively be discriminated by the transition from a reaction rate‐limited regime to an intraparticle diffusion‐limited regime. The effectiveness factor for competing kinetic models sometimes follows notably different trends versus reactant concentration. Therefore, taking the effectiveness factor into account provides one with an instrument for the selection of the most realistic kinetic model. The proof of concept is demonstrated using exemplary kinetics of the methanol dehydration over a commercially available activated γ ‐alumina catalyst. Methanol dehydration is an important commercial process since it produces a valuable chemical, which is dimethyl ether. It has been shown previously that this process follows the Langmuir–Hinshelwood kinetics with either dissociative or associative methanol adsorption. With the utilization of the intraparticle diffusion approach, it is demonstrated that only a dissociative path is appropriate. The problem of the experimental evaluation of the effectiveness factor and the limitations of the approach are also discussed.