Is kinetic molecular sieving of hydrogen isotopes feasible?

Kumar, A.V.Anil and Bhatia, Suresh K. (2008) Is kinetic molecular sieving of hydrogen isotopes feasible?. The Journal of Physical Chemistry Part C: Nanomaterials and Interfaces, 112 30: 11421-11426. doi:10.1021/jp8015358


Author Kumar, A.V.Anil
Bhatia, Suresh K.
Title Is kinetic molecular sieving of hydrogen isotopes feasible?
Journal name The Journal of Physical Chemistry Part C: Nanomaterials and Interfaces   Check publisher's open access policy
ISSN 1932-7447
Publication date 2008-01-01
Year available 2008
Sub-type Article (original research)
DOI 10.1021/jp8015358
Open Access Status
Volume 112
Issue 30
Start page 11421
End page 11426
Total pages 6
Editor G. C. Schatz
Place of publication United States of America
Publisher American Chemical Society
Language eng
Subject C1
960202 Atmospheric Processes and Dynamics
090401 Carbon Capture Engineering (excl. Sequestration)
Abstract We investigate the possibility of kinetic molecular sieving of hydrogen isotopes by studying their dynamical properties in the one-dimensional channels of microporous aluminophosphate AIPO(4)-25 at low temperatures. We use transition state theory as well as molecular dynamics simulations, using an effective quantum potential obtained via the Feynman-Hibbs path integral formalism. With the help of the free energy profile and barrier determined using the Widom particle insertion method, we demonstrate that transition state theory offers an effective and convenient method to determine self-diffusion coefficients, showing excellent agreement with those obtained from molecular dynamics simulations. Quantum-effect-induced kinetic molecular sieving, in which the heavier isotope (deuterium) diffuses faster than the lighter hydrogen, is observed at low temperature, consistent with our simulation results for narrow window zeolite-rho, and experimental evidence with 3 A carbon molecular sieve in the recent literature. The free energy profile provides insight into this remarkable counterintuitive behavior, showing that at sufficiently low temperature the free energy barrier for diffusion is smaller for deuterium than hydrogen and exhibits inverse temperature dependence. These findings suggest low-temperature kinetic molecular sieving of hydrogen isotopes as an attractive route for their separation.
Formatted abstract
We investigate the possibility of kinetic molecular sieving of hydrogen isotopes by studying their dynamical properties in the one-dimensional channels of microporous aluminophosphate AlPO 4-25 at low temperatures. We use transition state theory as well as molecular dynamics simulations, using an effective quantum potential obtained via the Feynman−Hibbs path integral formalism. With the help of the free energy profile and barrier determined using the Widom particle insertion method, we demonstrate that transition state theory offers an effective and convenient method to determine self-diffusion coefficients, showing excellent agreement with those obtained from molecular dynamics simulations. Quantum-effect-induced kinetic molecular sieving, in which the heavier isotope (deuterium) diffuses faster than the lighter hydrogen, is observed at low temperature, consistent with our simulation results for narrow window zeolite-ρ, and experimental evidence with 3 Å carbon molecular sieve in the recent literature. The free energy profile provides insight into this remarkable counterintuitive behavior, showing that at sufficiently low temperature the free energy barrier for diffusion is smaller for deuterium than hydrogen and exhibits inverse temperature dependence. These findings suggest low-temperature kinetic molecular sieving of hydrogen isotopes as an attractive route for their separation.
Keyword Transition-state Theory
Liquid Para-hydrogen
Chemical-reactions
Carbon Nanotubes
diffusion
Adsorption
Dynamics
Deuterium
Zeolites
Silicalite
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: 2009 Higher Education Research Data Collection
School of Chemical Engineering Publications
 
Versions
Version Filter Type
Citation counts: TR Web of Science Citation Count  Cited 22 times in Thomson Reuters Web of Science Article | Citations
Scopus Citation Count Cited 21 times in Scopus Article | Citations
Google Scholar Search Google Scholar
Created: Wed, 08 Apr 2009, 00:39:34 EST by Katherine Montagu on behalf of School of Chemical Engineering