Quantum Effect-Mediated Hydrogen Isotope Mixture Separation in Slit Pore Nanoporous Materials

Wang, Y. and Bhatia, S. K. (2009) Quantum Effect-Mediated Hydrogen Isotope Mixture Separation in Slit Pore Nanoporous Materials. JOURNAL OF PHYSICAL CHEMISTRY C, 113 33: 14953-14962. doi:10.1021/jp9044397


Author Wang, Y.
Bhatia, S. K.
Title Quantum Effect-Mediated Hydrogen Isotope Mixture Separation in Slit Pore Nanoporous Materials
Journal name JOURNAL OF PHYSICAL CHEMISTRY C   Check publisher's open access policy
ISSN 1932-7447
Publication date 2009-08
Year available 2009
Sub-type Article (original research)
DOI 10.1021/jp9044397
Volume 113
Issue 33
Start page 14953
End page 14962
Total pages 10
Editor Schatz , G. C.
Place of publication Washington, USA
Publisher American Chemical Society
Collection year 2010
Language eng
Subject C1
970109 Expanding Knowledge in Engineering
090404 Membrane and Separation Technologies
Abstract We use path integral simulations to investigate the separation of H-2 and HD, as well as H-2 and D-2, in carbon slit pores of various sizes using a new improved set of carbon-hydrogen interaction parameters determined in our laboratory. As expected, the selectivity of HD over H-2 is lower than that of D-2 over H-2 at the same conditions due to the smaller mass of HD molecules and hence larger quantum effects, In the pressure range of 0.1-10.0 bar, the selectivity is not sensitive to the pressure at the temperature of 77 K. At 40 K the selectivity shows a positive relation to the adsorbed phase density. We also report all unusual crossover effect in which the selectivity in a pore of width 0.85 nm exceeds that in a smaller pore (0.69 nm) at high densities due to enhanced quantum confinement effects when a second layer forms in the larger pore. The optimal pore widths for HD/H-2 separations were identified to be 0.56-0.57 nm, with operating pressures of 10.0 and 0.1 bar for the two pore sizes, respectively. We also simulate equilibrium separation in the commercial Takeda 3 angstrom carbon molecular sieve, based on a slit-like pore model with a distribution of pore sizes, but find only modest equilibrium selectivity for HD over H-2). It is suggested that while quantum effects are small within the pore bodies, narrow pore entrances must lead to significant quantum effects on the dynamics in order to explain literature data of faster uptake of D-2 compared to H-2 at 77 K in this material. Thus, kinetic molecular sieving at narrow necks. for which this material is well established, maybe a more attractive option than equilibrium separation. Alternatively, materials with controlled smaller pore sizes ire needed for more efficient equilibrium HD/H-2) separation. The ideal adsorption solution theory (IAST) is also examined for prediction of the binary hydrogen isotope mixture isotherms in the presence of quantum effects and is found to match simulations at all operating conditions investigated.
Keyword PATH-INTEGRAL SIMULATIONS
WALLED CARBON NANOTUBES
CANONICAL MONTE-CARLO
ADSORPTION
H-2
D-2
THERMODYNAMICS
NANOHORNS
Q-Index Code C1
Q-Index Status Confirmed Code

Document type: Journal Article
Sub-type: Article (original research)
Collections: 2010 Higher Education Research Data Collection
School of Chemical Engineering Publications
 
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Created: Thu, 03 Sep 2009, 07:42:20 EST by Mr Andrew Martlew on behalf of School of Chemical Engineering