(529b) Diffusion of CH4 and N2 in a Reduced Pore-Zorite (Ba-RPZ)

Ba-RPZ is a titanosilcate adsorbent that shows excellent kinetic selectivity for CH₄/N₂ separations [1]. Single component N₂ and CH₄ equilibrium loadings were measured on crystalline Ba-RPZ between 1 mbar to 1.2 bar and 30, 50 and 70°C using low pressure volumetry. The isosteric heat of adsorption was calculated using the collected equilibrium data. The isosteric heat of adsorption shows that both CH₄ and N₂ sees the Ba-RPZ surface as energetically homogenous. The equilibrium data for all components were fit to a single or dual site Langmuir isotherm. Mass transfer parameters for Ba-RPZ and zeolite 4A were measured for N₂ (at -20, -10 and 0°C) and CH₄ (at 30, 40 and 50°C) using a commercial volumetric apparatus. The measured uptake profiles show that diffusion of N₂ into Ba-RPZ is very fast. The CH₄ uptake profiles were fitted to a range of micropore models that describe resistance at the pore mouth, resistance within the micropores of the solid and a dual resistance model that assumes both the pore mouth and micropores contribute to the mass transfer resistance. It was found that mass transfer resistance mechanism of CH₄ in Ba-RPZ is best described by the dual resistance model. Collected diffusion parameters for both surface resistance and micropore resistance show a strong concentration dependence.