(660c) Novel Approach for Kinetic Measurements for Low Capacity Adsorbents | AIChE

(660c) Novel Approach for Kinetic Measurements for Low Capacity Adsorbents


Mangano, E. - Presenter, University of Edinburgh
Kalbassi, M. A., Air Products PLC
Whitley, R., Air Products & Chemicals Inc
Brandani, S., University of Edinburgh
The key advantage of the Zero Length Column (ZLC) technique is the capability to characterise an adsorbent, both from the equilibrium and kinetic point of view, by using less than 10 mg of sample, more rapidly and accurately than other conventional methods. Determination of the kinetics and transport mechanism may be prevented in some cases when the adsorption capacity of the sample is relatively low. In these cases, the decoupling of the kinetics of adsorption from the kinetics of the system becomes quite difficult due to the fact that the ZLC response curve is too close to the response of the system with no adsorbent. This means that it is not possible to rely on the traditional asymptotic method to extract any meaningful kinetic information in such systems.

Here we present a novel ZLC approach specifically developed to overcome this issue. The method is based on the measurement of the adsorption capacity at different adsorption times and relates this to the approach of the system to saturation. The new methodology was validated by measuring the kinetics of adsorption of N2 in 4A at very low temperatures (down to -20 °C). A cryogenic cell, purposely designed for ZLC tests at very low temperatures, was used for these experiments. The study was also extended at different temperatures to extract the activation energy of the diffusion process. The new methodology represents an easy alternative to the traditional ZLC approach which allows to overcome the limitations experienced when working with systems characterised by low adsorption capacity.