The Use of Low Temperature van der Waals Adsorption Isotherms in Determining the Surface Area of Iron Synthetic Ammonia Catalysts

Emmett, P. H.; Brunauer, Stephen

doi:10.1021/ja01287a041

Cited by 509 publications

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“…Using the above correlations and the t-surface areas as derived from the N 2 -physisorption measurements the surface coverage of H 2 at 1 bar can be calculated, if the average area occupied by one H 2 molecule (a M ) is known. Following the approach of Emmett and Brunauer [21], we estimated a M to be 0.14 nm 2 . With this a monolayer capacity for H 2 can be calculated as 7 × 10 18 molecules/m 2 .…”

Section: Resultsmentioning

confidence: 99%

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Hydrogen storage using physisorption – materials demands

et al. 2001

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Abstract.A survey is presented of the storage capacities of a large number of different adsorbents for hydrogen at 77 K and 1 bar. Results are evaluated to examine the feasibility and perspectives of transportable and reversible storage systems based on physisorption of hydrogen on adsorbents. It is concluded that microporous adsorbents, e.g. zeolites and activated carbons, display appreciable sorption capacities. Based on their micropore volume (∼ 1 ml/g) carbonbased sorbents display the largest adsorption, viz. 238 ml (STP)/g, at the prevailing conditions. Optimization of sorbent and adsorption conditions is expected to lead to adsorption of ∼ 560 ml (STP)/g, close to targets set for mobile applications. In the last two decades there has been an increasing interest in the development of (transportable) reversible systems for hydrogen storage with a high capacity, which is critical to the large-scale application of hydrogen fuel cells, in particular for mobile applications [1]. Up to now focus has mostly been on liquid-hydrogen and metal-hydride systems, which both have low energy efficiencies [2]. A higher energy efficiency is attainable with systems in which hydrogen is concentrated by physical adsorption above 70 K using a suitable adsorbent [3][4][5]. Such an absorbent should be safe, light and cheap and of course have a high adsorption capacity. In order to obtain a suitable driving range for automotive applications the United States Department of Energy (DOE) target has been set to 6.5 wt %, which equals 720 ml (STP)/g adsorbent . Schwarz and co-workers [6-8] studied the applicability of molecularly engineered activated carbons and came up with promising results. Much excitement has arisen on recent reports on the use of carbon nanofibers [9] and carbon nanotubes [10,11] In this paper we present a survey of the storage capacity for hydrogen at 77 K and 1 bar of a large number of different types of adsorbents -silicas, aluminas, zeolites, graphite, activated carbons and carbon nanofibers -in a wide range of specific surface areas and of different textures, in order to give further direction to our research on the development of a suitable storage system. PACS

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Section: Resultsmentioning

confidence: 99%

“…Activated graphite (3,9) is synthetic graphite that has been activated in the same way as described for the activated carbons. Carbon nanofibers (2,4,10,21) have been catalytically synthesized. They consist of conical (fishbone, 2, 4, 10) or tubular (parallel, 21) graphite planes [17].…”

Section: Methodsmentioning

confidence: 99%

Hydrogen storage using physisorption – materials demands

et al. 2001

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“…determination of the effective monolayer capacity of the MOF sample is done using the Point-B method. 22 The "effective monolayer" includes the region corresponding to adsorption after the gate-opening transition. We note that the linear extrapolation shown in Figure 3 is carried out at pressures above that of the gate-opening pressure for this temperature.…”

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O₂Adsorption on ZIF-8: Temperature Dependence of the Gate-Opening Transition

et al. 2014

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We present the results of an adsorption isotherm study of O 2 on the metal-organic framework ZIF-8. This material undergoes a structural transition ("gate-opening") as a function of increasing pressure and sorbent loading which manifests itself in the isotherm data as a quasivertical substep. We used this feature to explore the temperature dependence of the structural transition; we have found that the transition occurs below the saturated vapor pressure only for temperatures below 93.93 K. The adsorption isotherm data measured at various temperatures was used also to determine the isosteric heat of adsorption of O 2 on this sorbent for different sorbent loading values. We have studied the adsorption kinetics for this system, i.e., how the equilibration times for adsorption change as a function of sorbent loading. The sorbent loading dependence of the equilibration time is non-monotonic; this characteristic appears to be related to the structural transition in the sorbent.

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“…The best known method for determining the specific surface area of porous solids is obtained from the work of Brunauer, Emmitt, and Teller (BET) (11)(12)(13). The method is based on the determination of the number of molecules of gas which, when adsorbed on the surface of a solid, completely cover the solid with a monolayer of the gaS.…”

Section: B Measurement Of Coal Surface Areamentioning

confidence: 99%

Physical changes in the pore structure of coal with chemical processing

Harris¹

1978

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The Use of Low Temperature van der Waals Adsorption Isotherms in Determining the Surface Area of Iron Synthetic Ammonia Catalysts

Abstract: first discontinuity with respect to water content, considering the 4% point as the lowest percentage water content gel obtainable without destruction of gel activity. Calculating the area covered by 0.04 g. of water one molecule thick also gives a value of about 1 X 10s sq. cm.

Cited by 509 publications

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Hydrogen storage using physisorption – materials demands

Hydrogen storage using physisorption – materials demands

O₂Adsorption on ZIF-8: Temperature Dependence of the Gate-Opening Transition

Physical changes in the pore structure of coal with chemical processing

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The Use of Low Temperature van der Waals Adsorption Isotherms in Determining the Surface Area of Iron Synthetic Ammonia Catalysts

Abstract: first discontinuity with respect to water content, considering the 4% point as the lowest percentage water content gel obtainable without destruction of gel activity. Calculating the area covered by 0.04 g. of water one molecule thick also gives a value of about 1 X 10s sq. cm.

Cited by 509 publications

References 0 publications

Hydrogen storage using physisorption – materials demands

Hydrogen storage using physisorption – materials demands

O2Adsorption on ZIF-8: Temperature Dependence of the Gate-Opening Transition

Physical changes in the pore structure of coal with chemical processing

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O₂Adsorption on ZIF-8: Temperature Dependence of the Gate-Opening Transition