Influence of NaA Zeolite Crystal Expansion/Contraction on Zeolite Membrane Separations

Journal Article · Fri Dec 31 23:00:00 EST 2010 · Journal of Membrane Science

DOI:https://doi.org/10.1016/j.memsci.2010.10.043· OSTI ID:993454

Sorenson, Stephanie G ^[1]; Payzant, E Andrew ^[2]; Gibbons, Will T ^[1]; Soydas, Belma ^[1]; Kita, Hidetoshi ^[3]; Noble, Richard D ^[1]; Falconer, John L. ^[1]

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1. University of Colorado, Boulder
2. ORNL
3. Yamaguchi University, Japan

In-situ powder XRD measurements showed that the NaA zeolite unit cell contracts and expands upon adsorption, and these changes in zeolite crystal size correlate with permeation changes through NaA zeolite membranes. These membranes had high pervaporation selectivities, even though gas permeation was mainly through defects, as indicated by Knudsen selectivities for gases. At 300 K and a thermodynamic activity of 0.03, water contracted the NaA crystals by 0.22 vol%, and this contraction increased the helium flux through two NaA membranes by approximately 80%. Crystal contraction also increased the fluxes of i-butane during vapor permeation and i-propanol (IPA) during pervaporation (~ 0.03 wt% water). At activities above 0.07, water expanded NaA crystals and correspondingly decreased the membrane fluxes of helium, i-butane, and IPA. Similarly, methanol contracted NaA crystals by 0.05 vol% at an activity of 0.02, and this contraction slightly increased the helium and i-butane fluxes through a NaA membrane. Above an activity of 0.06, methanol expanded the crystals, and the fluxes of helium and i-butane through a NaA membrane decreased. The adsorbate-induced changes explain some pervaporation behavior reported by others, and they indicate that crystal expansion and contraction may increase or decrease zeolite NaA membrane selectivity by changing the defect sizes.

• Research Organization: Oak Ridge National Laboratory (ORNL); Center for Nanophase Materials Sciences
• Sponsoring Organization: SC USDOE - Office of Science (SC)
• DOE Contract Number: AC05-00OR22725
• OSTI ID: 993454
• Journal Information: Journal of Membrane Science, Journal Name: Journal of Membrane Science Journal Issue: 1-2 Vol. 366; ISSN 0376-7388
• Country of Publication: United States
• Language: English

Related Subjects

10 SYNTHETIC FUELS
ADSORPTION
CONTRACTION
DEFECTS
GASES
HELIUM
MEMBRANES
METHANOL
NEUTRON ACTIVATION ANALYSIS
THERMODYNAMIC ACTIVITY
WATER
X-RAY DIFFRACTION
ZEOLITES
in-situ x-ray diffraction
zeolites