Letter to the editor: Diffusion under pore saturation conditions

In the article "Diffusion Under Pore Saturaton Conditions", Lettat et al. (1) presents a model to describe mixture diffusion in MFI zeolite under conditions of pore saturation. As a motivation for developing their model they remark ‘‘the classical adsorbed-phase diffusion models based on the Maxwell-Stefan (M-S) equation cannot represent correctly multicomponent diffusion close to saturation’’, citing a variety of articles published prior to 2005 (2-5). In this Letter, we take issue with this remark. We also have reservations about the modifications that they have introduced in reformulating M-S equations, based on their perceived shortcomings of our published work in this area.