Zeolite Rho: a highly selective adsorbent for CO<sub>2</sub>/CH<sub>4</sub>separation induced by a structural phase modification

Palomino, Miguel; Corma, Avelino; Jordá, José L.; Rey, Fernando; Valencia, Susana

doi:10.1039/c1cc16320e

Cited by 147 publications

(186 citation statements)

References 31 publications

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“…[14][15][16] Recent computational studies have demonstrated that extraframework cations can move in the presence of CO 2 , 17 making cation gating effects possible. [18][19][20][21][22][23][24] In the postulated 'trapdoor' mechanism, cations occupying window sites permit the passage of molecules such as CO 2 or H 2 O that interact strongly with cations but block the windows to molecules that interact more weakly (such as CH 4 or N 2 ). These 'trapdoor' 3 zeolites adsorb CO 2 from mixtures of CH 4 or N 2 with very high selectivity.…”

Section: Introductionmentioning

confidence: 99%

“…These 'trapdoor' 3 zeolites adsorb CO 2 from mixtures of CH 4 or N 2 with very high selectivity. Zeolites A 18,19 and chabazite 20,21 with particular cation compositions have been suggested to demonstrate such behaviour, as have certain forms of zeolite Rho [22][23][24] and structures related to Rho. 25,26 In zeolite Rho, 27 large lta cages are linked by double 8-ring structural units, which act as windows and are also the favoured sites for large univalent cations such as Na + , K + and Cs + (8-ring refers to a ring of 8 framework metal atoms and 8 oxygen atoms).…”

Section: Introductionmentioning

confidence: 99%

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Cation Control of Molecular Sieving by Flexible Li-Containing Zeolite Rho

et al. 2016

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The adsorption of CO 2 on zeolite Li-Rho (unit cell composition Li 9.8 Al 9.8 Si 38.2 O 96 ) has been investigated by the measurement of adsorption isotherms (273 -300 K), breakthrough curves with a CO 2 /CH 4 /He mixture (308 K) and in situ synchrotron X-ray powder diffraction in CO 2 (298 K). The Rho framework distorts when in the Li-form to give a shape selective adsorbent for CO 2 over CH 4 , although breakthrough curves reveal diffusional limitations. In situ synchrotron powder XRD follows the expansion of the Li-Rho unit cell upon adsorption, which remains single phase to a CO 2 pressure of ca. 0.6 bar. Partial cation exchange of Li-2 Rho by Na + or Cs + gives two series of M,Li-Rho zeolites (M = Na, Cs). Where the occupancy of window sites (8R, D8R) between lta cages is less than 50%, hysteresis is not observed in CO 2 isotherms at 298 K. For Cs 1.8 Li 8 -Rho, which has a larger unit cell and a wider window than zeolite Li-Rho due to the presence of large Cs + cations in double 8-ring sites, breakthrough curves indicate faster CO 2 diffusion without significant loss of selectivity. We propose this control of adsorption kinetics of the flexible zeolite Rho via modification of cation content as a mechanism for cation controlled molecular sieving.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Cation Control of Molecular Sieving by Flexible Li-Containing Zeolite Rho

et al. 2016

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“…Typically, moderate selectivity for CO 2 over N 2 or CH 4 can be achieved over cationic zeolites such as Na-X [4] or Na-A [5], which result from the quadrupole moment of CO 2 and its polarisability. Recently, however, small pore zeolites of specific structures and compositions have been found to show very high selectivity for CO 2 over less polar gases such as CH 4 and N 2 due to a molecular 'trapdoor' effect that makes them strong candidates as sorbents for carbon capture [6][7][8][9][10][11][12].…”

Section: Introductionmentioning

confidence: 99%

“…[6] and K-, Rb-and Cs-chabazite [11,12] are examples of the former, Na-, K-, and Cs-forms of zeolite Rho [7][8][9][10] are examples of the latter. The presence of D8R windows in zeolite Rho, together with the ability of its framework to distort strongly, allows the D8R sites to bind the cations more closely, and permits trapdoor behaviour to occur up to higher gas pressures.…”

Section: Introductionmentioning

confidence: 99%

Structural changes of synthetic paulingite (Na,H-ECR-18) upon dehydration and CO₂ adsorption

Greenaway

Shin

Cox

et al. 2015

Zeitschrift Für Kristallographie - Crystalline Materials

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Abstract:The structure of dehydrated calcined ECR-18, synthetic paulingite, topology type PAU, unit cell composition Na 132 H 28 Si 512 Al 160 O 1344 , has been determined by Rietveld refinement against synchrotron X-ray powder diffraction data. Upon dehydration the symmetry of Na,H-ECR-18 changes from 3 Im m to 43 , m I with a corresponding decrease of cubic unit cell a parameter from 34.89412(1) Å to 33.3488(3) Å. This occurs as the framework distorts to afford closer coordination of Na + cations by framework O atoms in 8-ring window sites of the seven cage types present. Na + cations in 8R sites block the access of N 2 molecules to the internal pore space at 77 K but CO 2 adsorption at 308 K is observed, and is postulated to occur via a 'trapdoor' mechanism. In situ PXRD during CO 2 adsorption at pressures up to 10 bar show reversible broadening of diffraction peaks that is attributed to local crystallographic strain.

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“…Zeolites were synthesized at the Instituto de Tecnología Química in Valencia, according to procedures reported in literature [32,33,34], with a Si/Al molar ratio of 5 and the properties that are summarized in Table 1. parameter.…”

Section: Preparation Of MMMmentioning

confidence: 99%

Permselectivity improvement in membranes for CO2/N2 separation

Fernández-Barquín

Casado-Coterillo

Palomino

et al. 2016

Separation and Purification Technology

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In this work, small-pore zeolites of different topology (CHA, LTA5, Rho), all with Si/Al ratio of 5, have been added to highly permeable poly(1-trimethylsilyl-1-propyne) (PTMSP) to increase its selectivity and thermal and mechanical stability. Membranes were characterized by TGA, XRD, SEM and CO2 and N2 single gas permeation measurements at different temperatures. TGA reveal that the thermal resistance of the membranes is as good as pure PTMSP polymer. XRD and SEM results reflect that there is good interaction between the fillers and the membrane matrix, at 5 and 10 wt. % zeolite loadings, while at 20 wt.% a dual layer stucture is formed, when Rho zeolite is the filler, because the particle size of Rho is higher than those of LTA5 or CHA, and voids appear that limit the permselectivity performance. In single gas permeation of N2 and CO2, the influence of temperature, zeolite loading and type is analyzed. The selectivity of pure PTMSP is considerably enhanced with the addition of the zeolites and the increase of temperature, and the MMM loaded with 5 wt. % zeolite surpassed the Robeson's upper bound for CO2/N2 separation, without decreasing the permeability too much. Upon increasing temperature from 298 to 333 K, the permselectivity is enhanced even further without loss of permeability. The 5 wt% loaded membranes were tested in CO2/N2 mixed gas separation experiments at 333 K and 12.5 wt. % CO2 in the feed, and the permselectivity of LTA5-and Rho-PTMSP membranes was further enhanced, compared with the single gas permeation experiments.

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Zeolite Rho: a highly selective adsorbent for CO₂/CH₄separation induced by a structural phase modification

Cited by 147 publications

References 31 publications

Cation Control of Molecular Sieving by Flexible Li-Containing Zeolite Rho

Cation Control of Molecular Sieving by Flexible Li-Containing Zeolite Rho

Structural changes of synthetic paulingite (Na,H-ECR-18) upon dehydration and CO₂ adsorption

Permselectivity improvement in membranes for CO2/N2 separation

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Zeolite Rho: a highly selective adsorbent for CO2/CH4separation induced by a structural phase modification

Cited by 147 publications

References 31 publications

Cation Control of Molecular Sieving by Flexible Li-Containing Zeolite Rho

Cation Control of Molecular Sieving by Flexible Li-Containing Zeolite Rho

Structural changes of synthetic paulingite (Na,H-ECR-18) upon dehydration and CO2 adsorption

Permselectivity improvement in membranes for CO2/N2 separation

Contact Info

Product

Resources

About

Zeolite Rho: a highly selective adsorbent for CO₂/CH₄separation induced by a structural phase modification

Structural changes of synthetic paulingite (Na,H-ECR-18) upon dehydration and CO₂ adsorption