Digital Adsorption: 3D Imaging of Gas Adsorption Isotherms by X-ray Computed Tomography

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Title: Digital Adsorption: 3D Imaging of Gas Adsorption Isotherms by X-ray Computed Tomography
Author(s): Joss, L
Pini, R
Item Type: Journal Article
Abstract: We report on a novel approach for the measurement of gas adsorption in microporous solids using X-ray computed tomography (CT) that we refer to as digital adsorption. Similar to conventional macroscopic methods, the proposed protocol combines observations with an inert and an adsorbing gas to produce equilibrium isotherms in terms of the truly measurable quantity in an adsorption experiment, namely the surface excess. Most significantly, X-ray CT allows probing the adsorption process in three dimensions, so as to build spatially-resolved adsorption isotherms with a resolution of approximately 10 mm3 within a fixed-bed column. Experiments have been carried out at 25 C and in the pressure range 1-30bar using CO2 on activated carbon, zeolite 13X and glass beads (as control material), and results are validated against literature data. A scaling approach was applied to analyze the whole population of measured adsorption isotherms (~7600), leading to single universal adsorption isotherm curves that are descriptive of all voxels for a given adsorbate-adsorbent system. By analyzing the adsorption heterogeneity at multiple length scales (1 mm3 to 1 cm3), packing heterogeneity was identified as the main contributor for the larger spatial variability in the adsorbed amount observed for the activated carbon rods as compared to zeolite pellets. We also show that this technique is readily applicable to a large spectrum of commercial porous solids, and that it can be further extended to weakly adsorbing materials with appropriate protocols that reduce measurement uncertainties. As such, the obtained results prove the feasibility of digital adsorption and highlight substantial opportunities for its wider use in the field of adsorptive characterization of porous solids.
Publication Date: 7-Nov-2017
Date of Acceptance: 7-Nov-2017
ISSN: 1932-7447
Publisher: American Chemical Society
Start Page: 26903
End Page: 26915
Journal / Book Title: The Journal of Physical Chemistry Part C: Nanomaterials and Interfaces
Volume: 121
Issue: 48
Copyright Statement: Copyright © 2017 American Chemical Society
Sponsor/Funder: Qatar Petroleum
Funder's Grant Number: N/A
Copyright Statement: Copyright © 2017 American Chemical Society
Keywords: Science & Technology
Physical Sciences
Chemistry, Physical
Nanoscience & Nanotechnology
Materials Science, Multidisciplinary
Science & Technology - Other Topics
Materials Science
09 Engineering
03 Chemical Sciences
10 Technology
Physical Chemistry
Publication Status: Published
Appears in Collections:Faculty of Engineering
Chemical Engineering

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