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Title: Kr/Xe Separation over a Chabazite Zeolite Membrane

Abstract

Cryogenic distillation, the current conventional technology to separate Krypton and Xenon from air, and from nuclear reprocessing technologies, is an energy-intensive and expensive process. Membrane technology could potentially make this challenging industrial separation less energy intensive and economically viable. We demonstrate that chabazite zeolite SAPO-34 membranes effectively separated Kr/Xe gas mixtures at industrially relevant compositions. Control over membrane thickness and average crystal size led to industrial range permeances and high separation selectivities. Specifically, SAPO-34 membranes can separate Kr/Xe mixtures with Kr permeances as high as 361.4 GPU and separation selectivities of 34.8 for molar compositions close to typical concentrations of these two gases in air. In addition, SAPO-34 membranes separated Kr/Xe mixtures with Kr permeances as high as 525.7 GPU and separation selectivities up to 45.1 for molar compositions as might be encountered in nuclear reprocessing technologies. Molecular sieving and differences in diffusivities were identified as the dominant separation mechanisms.

Authors:
; ; ; ; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1355102
Report Number(s):
PNNL-SA-121268
Journal ID: ISSN 0002-7863; 830403000
DOE Contract Number:
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of the American Chemical Society; Journal Volume: 138; Journal Issue: 31
Country of Publication:
United States
Language:
English

Citation Formats

Feng, Xuhui, Zong, Zhaowang, Elsaidi, Sameh K., Jasinski, Jacek B., Krishna, Rajamani, Thallapally, Praveen K., and Carreon, Moises A.. Kr/Xe Separation over a Chabazite Zeolite Membrane. United States: N. p., 2016. Web. doi:10.1021/jacs.6b06515.
Feng, Xuhui, Zong, Zhaowang, Elsaidi, Sameh K., Jasinski, Jacek B., Krishna, Rajamani, Thallapally, Praveen K., & Carreon, Moises A.. Kr/Xe Separation over a Chabazite Zeolite Membrane. United States. doi:10.1021/jacs.6b06515.
Feng, Xuhui, Zong, Zhaowang, Elsaidi, Sameh K., Jasinski, Jacek B., Krishna, Rajamani, Thallapally, Praveen K., and Carreon, Moises A.. 2016. "Kr/Xe Separation over a Chabazite Zeolite Membrane". United States. doi:10.1021/jacs.6b06515.
@article{osti_1355102,
title = {Kr/Xe Separation over a Chabazite Zeolite Membrane},
author = {Feng, Xuhui and Zong, Zhaowang and Elsaidi, Sameh K. and Jasinski, Jacek B. and Krishna, Rajamani and Thallapally, Praveen K. and Carreon, Moises A.},
abstractNote = {Cryogenic distillation, the current conventional technology to separate Krypton and Xenon from air, and from nuclear reprocessing technologies, is an energy-intensive and expensive process. Membrane technology could potentially make this challenging industrial separation less energy intensive and economically viable. We demonstrate that chabazite zeolite SAPO-34 membranes effectively separated Kr/Xe gas mixtures at industrially relevant compositions. Control over membrane thickness and average crystal size led to industrial range permeances and high separation selectivities. Specifically, SAPO-34 membranes can separate Kr/Xe mixtures with Kr permeances as high as 361.4 GPU and separation selectivities of 34.8 for molar compositions close to typical concentrations of these two gases in air. In addition, SAPO-34 membranes separated Kr/Xe mixtures with Kr permeances as high as 525.7 GPU and separation selectivities up to 45.1 for molar compositions as might be encountered in nuclear reprocessing technologies. Molecular sieving and differences in diffusivities were identified as the dominant separation mechanisms.},
doi = {10.1021/jacs.6b06515},
journal = {Journal of the American Chemical Society},
number = 31,
volume = 138,
place = {United States},
year = 2016,
month = 8
}
  • Natural chabazite zeolite has been selected as the baseline treatment technology to compare the performance of emerging sorbent materials for the removal of {sup 90}Sr and {sup 137}Cs from contaminated process water. The resorcinol-formaldehyde resin, developed at Savannah River Site, is the first sorbent to be evaluated in this study. This paper summarizes the required contact times for maximum strontium and cesium removal, presents sorption isotherms in wastewater simulant and authentic wastewater, and defines the effects of elevated concentrations of K, Mg, Ca, and Na in wastewater for both sorbents.
  • We have used the pair distribution function (PDF) method to gain insight into the mechanism of contraction of zeolite chabazite. Using this method we followed how the interatomic distances of the local structure changed with temperature. By optimization of the structure by free energy minimization and using the Reverse Monte Carlo technique we were able to find structural models at low and at high temperatures that agreed quantitatively with our experimental PDFs. From these models we conclude that the mechanism of contraction with temperature cannot involve rocking of the tetrahedra as rigid unit modes as there are distortions of themore » tetrahedra with temperature (indicating internal vibrations) and also that the mechanism of contraction probably involves a mode that translates along the Si-O3-Si-O4-Si linkages inside of the D6R of zeolite chabazite.« less
  • The locations of Li{sup +} and Na{sup +} cations in dehydrated chabazite were studied by neutron powder diffraction, {sup 7}Li and {sup 23}Na magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy, and {sup 23}Na multiple quantum MAS (MQMAS) NMR spectroscopy. Neutron powder diffraction data were collected on lithium chabazite (space group: R{bar 3}m, a = 9.3357(5){angstrom}, {alpha} = 93.482(4){degree}, R{sub wp} = 5.83%, R{sub p} = 4.65%, {sub {chi}}{sup 2} = 1.24) and on a mixed lithium sodium chabazite (space group: R{bar 3}m, a = 9.3385(5){angstrom}, {alpha} = 93.382(4){degree}, R{sub wp} = 5.94%, R{sub p} = 4.83%, {sub {chi}}{sup 2}more » = 1.27). Both neutron diffraction and {sup 7}Li MAS reveal lithium chabazite to have two cationic sites: one at the six-ring window of the hexagonal prism (SII) and one in the supercage at the four-ring window of the hexagonalprism (SIII). Mixed lithium-sodium chabazites reveal strong evidence of selective occupancy accompanied by concomitant rearrangement effects. While the introduction of sodium into lithium chabazite reduces occupation primarily at the SIII site, a decrease of the SII site lithium cation population is also observed at sodium levels above 24%. At low sodium content, sodium cations occupy a site in the eight-ring window of the channel (SIII{prime}). At sodium content around 70% and higher, sodium cations also reside at the SII sites vacated by the lithium cations. The increased population of SII sites by Na{sup +} is associated with a marked increase in the lattice constant. The implications of the observed site preferences for noncryogenic air separation are discussed.« less
  • A porous {alpha}-alumina support tube, polished with a finely powdered X-type zeolite for use as seeds, was placed vertically in an autoclave containing an aqueous mixture of water glass and sodium aluminate. Hydrothermal synthesis was carried out at 90 C for 24 h. A polycrystalline layer of Y-type zeolite was thus formed on the outer surface of the support tube. After washing and drying in air, permeances of single components and mixtures of CO{sub 2} and N{sub 2}, as well as CH{sub 4}, C{sub 2}H{sub 6}, and SF{sub 6}, were determined. The CO{sub 2} permeance was higher than that ofmore » N{sub 2} at temperatures of 30--130 C. When an equimolar mixture of CO{sub 2} and N{sub 2} was fed into the feed side, the CO{sub 2} permeance was nearly equal to that for the single-component system and the N{sub 2} permeance for the mixture was greatly decreased, especially at lower permeation temperatures. This was due to selective adsorption of CO{sub 2} in subnanometer micropores of the membrane. At 30 C, the permeance of CO{sub 2} was higher than 10{sup {minus}7} mol/m{times}Pa, and the permselectivity of CO{sub 2} to N{sub 2} was 20--100.« less