(677c) Variability of Adsorption Properties on HiSiV3000 Individual Pellets

The use of kinetic and equilibrium information extracted from mg-scale measurements to scale up adsorption processes is often considered questionable, due to the lack of homogeneity on commercial adsorbents from the same batch. This inhomogeneity may be caused mainly by large equipment and/or inappropriate treatment of materials during the manufacturing process¹. In this work we present a methodology for the quantification of variability and reproducibility through the measurement of the effective diffusivity of individual commercial pellets.

In this analysis, Zero Length Column (ZLC) measurements² are carried out on individual commercial HiSiv3000 extrudates from UOP, a Honeywell company. ZLC responses with ppm-levels of n-Pentane as a probe molecule are used for the characterization of the effective diffusivity following the recommended experimental protocol³. This allows the unequivocal determination of the effective macropore diffusivity and the Henry law constant through a campaign of experiments at different flowrates, using partial and full equilibration of the sample over a temperature range of 150-200ËšC.

To determine intra-batch variability, a number of randomly chosen pellets were examined under identical conditions with the ZLC. The moving average of the kinetic time and Henry law constants for each additional sample was monitored until stable values were obtained for both parameters. This completes the iterative process and the average values can be then extracted.

To demonstrate that these are representative of the properties of the larger batch, the average values were used to fully predict a breakthrough experiment using a sample 100 times larger carried out under the same conditions.

The results show an excellent match between the experimental curve and the model allowing also to determine the maximum deviation from the average values. Our approach confirms that for adsorbent materials of good quality single pellet characterization using the ZLC can be used to predict satisfactorily the behavior of a scaled-up process through a proper model implementation⁴ even in the worst possible scenario, i.e. for the individual pellet properties furthest from the average. The approach can be applied as a rapid tool to monitor the batch homogeneity during the quality control of manufactured adsorbents.

[1] Wilkins N. S., Rajendran A. & Farooq S. Dynamic column breakthrough experiments for measurement of adsorption equilibrium and kinetics. Adsorption 27, 397–422 (2021).

[2] Eic M. and Ruthven D.M. A new experimental technique for measurement of intracrystalline diffusivity. Zeolites 8, 40–45 (1988).

[3] Brandani S. & Mangano E. The Zero Length Column Technique to Measure Adsorption Equilibrium and Kinetics: Lessons Learnt from 30 Years of Experience. Adsorption 27, 319–351 (2021).

[4] Brandani F., Rouse A., Brandani S. & Ruthven, D. M. Adsorption Kinetics and Dynamic Behavior of a Carbon Monolith. Adsorption 10, 99–109 (2004).