Knudsen diffusion and viscous flow dusty-gas coefficients for pelletised zeolites from kinetic uptake experiments

A simple volumetric uptake apparatus was used to determine uptake data of N-2 on a sample of LiLSX zeolite for two different particle sizes, two temperatures, and a variety of different dosing pressure levels. Using a mass and energy conservation model for the dosing and sample volumes and the Dusty Gas Model + viscous flow for the mass transfer description at the pellet level, the Knudsen and viscous flow structural parameters were derived. Our analysis gave structural coefficients C-K = 0.0827 +/- 0.018 and C-v = 0.0608 +/- 0.026 which gave good agreement across all of the experimental runs conducted for both particle sizes and all pressure ranges. From these, tortuosity coefficients for Knudsen and viscous flow were derived and gave tau(K) = epsilon(P.macro)/C-K = 3.7 +/- 0.8 and tau(v) = epsilon(P.macro)/C-v = 5.1 +/- 2.2 respectively. These are in good agreement with reported values. The apparatus and procedure is not very sensitive to the viscous flow coefficient but is sensitive to the Knudsen coefficient. All other parameters of the model were measured or determined by calibration experiments. This study suggests that the apparatus may be useful for determination of some of the fundamental structural coefficients employed in the Dusty Gas Model.