Zeolites as media for hydrogen storage*1

Weitkamp, Jens; Fritz, Michael; Ernst, Stefan

doi:10.1016/0360-3199(95)00058-l

Cited by 316 publications

(117 citation statements)

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“…2,3 Storing hydrogen by chemical bonding or physisorption may circumvent these problems. Several storage media are considered, e.g., nanosized magnesium hydride, 4 physisorption on carbon, 5,6 and sodium alanate (NaAlH 4 ). 2,7 Sodium alanate is promising since its thermodynamic properties enable reversible storage of hydrogen at low temperatures for on-board applications.…”

Section: Introductionmentioning

confidence: 99%

Active Ti Species in TiCl₃-Doped NaAlH₄. Mechanism for Catalyst Deactivation

et al. 2007

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The nature of the active Ti species in TiCl 3 -doped NaAlH 4 , a promising hydrogen storage material, was studied as a function of the desorption temperature with Ti K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy, Ti K-edge X-ray absorption near-edge structure (XANES) spectroscopy, and X-ray diffraction (XRD). In the freshly prepared sample, Ti was amorphous and surrounded by 4.8 Al atoms divided between two shells at 2.71 and 2.89 Å. In the next shell, 1.9 Ti atoms were detected at 3.52 Å. It was concluded that 30% of Ti was incorporated into the surface of Al crystallites and 70% of Ti occupied interstitials in the NaAlH 4 lattice, possibly forming trimeric, triangular Ti entities. After hydrogen desorption at 125°C, NaAlH 4 decomposed and the Ti-Al coordination number increased from 4.8 to 8.5. We propose that all Ti is incorporated into the surface layer of the formed Al. After the material was heated to 225°C, the local structure of Ti, as inferred from EXAFS and XANES spectroscopy, was identical to the local structure of a TiAl 3 alloy. However, the formed alloy was amorphous and was only detected in XRD by an increase of the background intensity around the Al diffraction. These so-called "TiAl 3 clusters" agglomerated in the heat treatment to 475°C, forming crystalline TiAl 3 . Earlier work has shown that increasing the desorption temperature of NaAlH 4 lowers the absorption rate and capacity of hydrogen in the next step. Thus, by comparing our results with absorption properties published in the literature on similar samples, we could rank the activity of the Ti for hydrogen absorption as Ti in the Al surface > TiAl 3 cluster > crystalline TiAl 3 , therewith indicating that Ti incorporated into the surface of Al is the most active for the absorption of hydrogen.

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Section: Introductionmentioning

confidence: 99%

Active Ti Species in TiCl₃-Doped NaAlH₄. Mechanism for Catalyst Deactivation

et al. 2007

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“…[1][2][3] Porous solids for which the largest pore window openings have aperture dimensions similar to the kinetic diameter of hydrogen are especially interesting for hydrogen storage by means of encapsulation, i.e., trapping small gas molecules inside zeolitic cavities by changing the effective pore window opening to these cavities. This controlled encapsulation principle has previously been demonstrated in zeolites with respect to varying temperature, 4 and by application of an external force 5 to the material.…”

Section: Introductionmentioning

confidence: 99%

Molecular-dynamics analysis of the diffusion of molecular hydrogen in all-silica sodalite

Berg

Bromley

Flikkema

et al. 2004

The Journal of Chemical Physics

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In order to investigate the technical feasibility of crystalline porous silicates as hydrogen storage materials, the self-diffusion of molecular hydrogen in all-silica sodalite is modeled using large-scale classical molecular-dynamics simulations employing full lattice flexibility. In the temperature range of 700-1200 K, the diffusion coefficient is found to range from 1.6•10 Ϫ10 to 1.8•10 Ϫ9 m 2 /s. The energy barrier for hydrogen diffusion is determined from the simulations allowing the application of transition state theory, which, together with the finding that the pre-exponential factor in the Arrhenius-type equation for the hopping rate is temperature-independent, enables extrapolation of our results to lower temperatures. Estimates based on mass penetration theory calculations indicate a promising hydrogen uptake rate at 573 K.

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“…A possible route to avoid poisoning of the adsorbent is to employ size selective microporous materials such as zeolites either as a membrane for purification, or as an adsorbent for storage. The selective uptake and release of hydrogen in zeolites as adsorbents can be controlled relatively easily by altering temperature and pressure conditions 1 or by applying an external force on the material. 2 Sodalite, in particular, seems to be a suitable zeolitic framework type for hydrogen purification and adsorption because of its large void volume ͑0.35 cc/cc͒ ͑Ref.…”

Section: Introductionmentioning

confidence: 99%

“…The energy barrier of passing through a six-membered ring, however, can be overcome at elevated temperatures and molecular hydrogen can pass through. 1 This indicates that the sodalite can be loaded at high temperature and pressure and that the hydrogen can be encapsulated by cooling at that pressure. Heating the zeolite up at a lower pressure allows the hydrogen to escape from the zeolite again.…”

Section: Introductionmentioning

confidence: 99%

“…Heating the zeolite up at a lower pressure allows the hydrogen to escape from the zeolite again. 1 This process will be highly selective since the six-membered ring is just large enough for hydrogen passage and H 2 is one of the smallest of all molecules. If sodalite is used as a membrane, the purification will also be very selective for the same reason.…”

Section: Introductionmentioning

confidence: 99%

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Effect of cation distribution on self-diffusion of molecular hydrogen in Na3Al3Si3O12 sodalite: A molecular dynamics study

Berg

Bromley

Flikkema

et al. 2004

The Journal of Chemical Physics

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The diffusion of hydrogen in sodium aluminum sodalite ͑NaAlSi-SOD͒ is modeled using classical molecular dynamics, allowing for full flexibility of the host framework, in the temperature range 800-1200 K. From these simulations, the self-diffusion coefficient is determined as a function of temperature and the hydrogen uptake at low equilibrium hydrogen concentration is estimated at 573 K. The influence of the cation distribution over the framework on the hydrogen self-diffusion is investigated by comparing results employing a low energy fully ordered cation distribution with those obtained using a less ordered distribution. The cation distribution is found to have a surprisingly large influence on the diffusion, which appears to be due to the difference in framework flexibility for different cation distributions, the occurrence of correlated hopping in case of the ordered distribution, and the different nature of the diffusion processes in both systems. Compared to our previously reported calculations on all silica sodalite ͑all-Si-SOD͒, the hydrogen diffusion coefficient of sodium aluminum sodalite is higher in the case of the ordered distribution and lower in case of the disordered distribution. The hydrogen uptake rates of all-Si-SOD and NaSiAl-SOD are comparable at high temperatures (ϳ1000 K) and lower for all-Si-SOD at lower temperatures (ϳ400 K).

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Zeolites as media for hydrogen storage*1

Cited by 316 publications

References 11 publications

Active Ti Species in TiCl₃-Doped NaAlH₄. Mechanism for Catalyst Deactivation

Active Ti Species in TiCl₃-Doped NaAlH₄. Mechanism for Catalyst Deactivation

Molecular-dynamics analysis of the diffusion of molecular hydrogen in all-silica sodalite

Effect of cation distribution on self-diffusion of molecular hydrogen in Na3Al3Si3O12 sodalite: A molecular dynamics study

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Zeolites as media for hydrogen storage*1

Cited by 316 publications

References 11 publications

Active Ti Species in TiCl3-Doped NaAlH4. Mechanism for Catalyst Deactivation

Active Ti Species in TiCl3-Doped NaAlH4. Mechanism for Catalyst Deactivation

Molecular-dynamics analysis of the diffusion of molecular hydrogen in all-silica sodalite

Effect of cation distribution on self-diffusion of molecular hydrogen in Na3Al3Si3O12 sodalite: A molecular dynamics study

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Active Ti Species in TiCl₃-Doped NaAlH₄. Mechanism for Catalyst Deactivation

Active Ti Species in TiCl₃-Doped NaAlH₄. Mechanism for Catalyst Deactivation