Hydrogen and carbon dioxide adsorption with tetra‐n‐butyl ammonium semi‐clathrate hydrates for gas separations |
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| Authors: | Hiroyuki Komatsu Masaki Ota Yoshiyuki Sato Masaru Watanabe Richard L Smith Jr |
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| Affiliation: | 1. Dept. of Chemistry and Chemical Engineering, Niigata University, Niigata, Japan;2. Graduate School of Engineering, Research Center of Supercritical Fluid Technology, Tohoku University, Sendai, Japan;3. Graduate School of Environmental Studies, Research Center of Supercritical Fluid Technology, Tohoku University, Sendai, Japan |
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| Abstract: | Gas adsorption rates of H2, CO2, and H2‐CO2 gas mixture (H2/CO2 = 3.4) with tetra‐n‐butyl ammonium salt (bromide, chloride, and fluoride) semi‐clathrate hydrate particles were measured at 269 K to assess their properties for gas separation. Equilibrium gas occupancies in the S‐cages of the particles were in order of (high to low) for hexagonal structure‐I, tetragonal structure‐I, and superlattice of cubic structure‐I structures with the maximum fractional occupancy by CO2 being about 40%. The CO2 diffusion rate depended on the anion size of the salt, which is attributed to distortion of the S‐cage that is close to the molecular size of CO2. Simulations of semi‐clathrate hydrate particles with theory showed that H2/CO2 selectivities could be as high as 36 (3.0 mol% TBAF) and that selectivities for an ideal membrane (3.3 mol% TBAF) could be >100 (269 K, 0.3–4.5 MPa). Semi‐clathrate hydrates have wide application as separation media for gas mixtures. © 2014 American Institute of Chemical Engineers AIChE J, 61: 992–1003, 2015 |
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| Keywords: | separations gas adsorption formation kinetics structure anion |
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