Efficient recovery of CO2 from flue gas by clathrate hydrate formation in porous silica gels

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Thermodynamic measurements and NMR spectroscopic analysis were used to show that it is possible to recover CO2 from flue gas by forming a mixed hydrate that removes CO2 preferentially from CO2/N-2 gas mixtures using water dispersed in the pores of silica gel. Kinetic studies with H-1 NMR microimaging showed that the dispersed water in the silica gel pore system reacts readily with the gas, thus obviating the need for a stirred reactor and excess water. Hydrate phase equilibria for the ternary CO2-N-2-water system in silica gel pores were measured, which show that the three-phase hydrate-water-rich liquid-vapor equilibrium curves were shifted to higher pressures at a specific temperature when the concentration of CO2 in the vapor phase decreased. C-13 cross-polarization NMR spectral analysis and direct measurement of the CO2 content in the hydrate phase suggested that the mixed hydrate is structure 1 at gas compositions of more than 10 mol % CO2, and that the CO2 molecules occupy mainly the more abundant 5(12)6(2) cages. This makes it possible to achieve concentrations of more than 96 mol % CO2 gas in the product after three cycles of hydrate formation and dissociation. H-1 NMR Microimaging showed that hydrate yields of better than 85%, based on the amount of water, could be obtained in 1 h when a steady state was reached, although similar to 90% of this yield was achieved after similar to 20 min of reaction time.
Publisher
AMER CHEMICAL SOC
Issue Date
2005-04
Language
English
Article Type
Article
Keywords

C-13 NMR-SPECTROSCOPY; X-RAY-DIFFRACTION; CARBON-DIOXIDE; PHASE-BEHAVIOR; DEUTERATED ICE; CAGE OCCUPANCY; METHANE; NUCLEATION; XE-129; GUEST

Citation

ENVIRONMENTAL SCIENCE & TECHNOLOGY, v.39, no.7, pp.2315 - 2319

ISSN
0013-936X
DOI
10.1021/es049269z
URI
http://hdl.handle.net/10203/3622
Appears in Collection
ME-Journal Papers(저널논문)CBE-Journal Papers(저널논문)
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