(662e) Diffusion of N2 and CO2 in 13X Zeolite From Volumetric Frequency Response Measurements Up to 10 Hz

Frequency response methods have been developed as an alternative technique for the determination of mass transfer mechanisms controlling the transport of gases into and out of microporous adsorbent materials. Recent results in the literature are showing that this technique seems to be the best for discriminating the controlling mechanism. It is also possible to reveal two or more different controlling mechanisms that may dominate in different frequency ranges.

The present talk will focus on the use of the volumetric frequency response (VFR) approach for the identification on the main mechanism governing the transport of N₂ and CO₂ in zeolite 13X.   In a recently commissioned VFR apparatus, experiments were carried out with pure gases at pressures of 200, 400 and 750 Torr, temperatures of 25, 40 and 55 ^oC and frequencies between 0.7×10^-5 and 10 Hz. The results show that the transport of both species is purely diffusive (non Darcinian) and that for the case of CO₂, the diffusive mechanism is consistent with macropore diffusion. The results also show that these mechanisms can be unequivocally identified under the unavoidable thermal affects that appear at lower frequencies. The results were used to show the dependency of the linear driving force (LDF) mass transfer coefficient on frequency in the regions where both the Glueckauf and Nakao/Suzuki approximations dominate.