Mass Transfer Mechanisms and Rates of CO2 and N2 in 13X Zeolite from Volumetric Frequency Response

The mass transfer mechanisms and rates of CO2 and N2 in 13X zeolite beads were determined using volumetric frequency response (VFR). The VFR experiments were conducted with each gas over a wide range of frequencies from 7x10-5 to 9.5 Hz at 100, 200 and 750 torr at 25 oC for CO2, and at 200, 400 and 750 torr at 25 oC, and at 40 and 55 oC at 400 torr for N2. The resulting experimental intensity response curves were fitted to four different non-isothermal mass transfer models, including micropore diffusion, macropore gas diffusion, macropore viscous (Poiseuille) flow and macropore surface diffusion. The resulting experimental phase lag response curves were predicted from the resulting model parameters. The macropore gas diffusion model fitted and predicted the experimental response curves the best for both gases, confirming the mass transport of both CO2 and N2 in 13X zeolite beads is macropore gas diffusion controlled. The corresponding diffusional time constants Dp/Rp2 were 3.32 s-1 for CO2 and 5.1 s-1 for N2.