Identification of Transport Mechanism in Adsorbent Micropores from Column Dynamics

The possibility of distinguishing between barrier and pore diffusional resistances in adsorbent micropores from dynamic column response has been explored. The modeling of transport through a barrier resistance confined at a micropore mouth is mathematically equivalent to the linear driving force (LDF) model. By comparing the pore diffusion and LDF models for dynamic column response for a linear isotherm, it is shown that the extent of agreement between the two models depends on the product of the two parameters α [= (1 − ε p ) K c /ε p ] and γ (= D c L / r c 2 v o ). By an appropriate choice of operating conditions, it is indeed possible to clearly distinguish between the two mechanisms. The proposed criteria have been verified experimentally for the breakthrough of oxygen and nitrogen in a 4A zeolite and two carbon molecular sieve samples.