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Abstract
A sound understanding of any sorption system requires an accurate determination of the enthalpy of adsorption. This is a fundamental thermodynamic quantity that can be determined from experimental sorption data and its correct calculation is extremely important for heat management in adsorptive gas storage applications. It is especially relevant for hydrogen storage, where porous adsorptive storage is regarded as a competing alternative to more mature storage methods such as liquid hydrogen and compressed gas. Among the most common methods to calculate isosteric enthalpies in the literature are the virial equation and the Clausius–Clapeyron equation. Both methods have drawbacks, for example, the arbitrary number of terms in the virial equation and the assumption of ideal gas behaviour in the Clausius–Clapeyron equation. Although some researchers have calculated isosteric enthalpies of adsorption using excess amounts adsorbed, it is arguably more relevant to applications and may also be more thermodynamically consistent to use absolute amounts adsorbed, since the Gibbs excess is a partition, not a thermodynamic phase. In this paper the isosteric enthalpies of adsorption are calculated using the virial, Clausius–Clapeyron and Clapeyron equations from hydrogen sorption data for two materials—activated carbon AX-21 and metal-organic framework MIL-101.
It is shown for these two example materials that the Clausius–Clapeyron equation can only be used at low coverage, since hydrogen’s behaviour deviates from ideal at high pressures. The use of the virial equation for isosteric enthalpies is shown to require care, since it is highly dependent on selecting an appropriate number of parameters. A systematic study on the use of different parameters for the virial was performed and it was shown that, for the AX-21 case, the Clausius–Clapeyron seems to give better approximations to the exact isosteric enthalpies calculated using the Clapeyron equation than the virial equation with 10 variable parameters.
It is shown for these two example materials that the Clausius–Clapeyron equation can only be used at low coverage, since hydrogen’s behaviour deviates from ideal at high pressures. The use of the virial equation for isosteric enthalpies is shown to require care, since it is highly dependent on selecting an appropriate number of parameters. A systematic study on the use of different parameters for the virial was performed and it was shown that, for the AX-21 case, the Clausius–Clapeyron seems to give better approximations to the exact isosteric enthalpies calculated using the Clapeyron equation than the virial equation with 10 variable parameters.
Original language | English |
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Pages (from-to) | 373-384 |
Number of pages | 12 |
Journal | Adsorption |
Volume | 20 |
Issue number | 2-3 |
DOIs | |
Publication status | Published - Feb 2014 |
Keywords
- isosteric enthalpies of adsorption
- hydrogen storage
- thermal management
- storage systems
- porous materials
- physisorption
Fingerprint
Dive into the research topics of 'Isosteric enthalpies for hydrogen adsorbed on nanoporous materials at high pressures'. Together they form a unique fingerprint.Projects
- 1 Finished
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UK SUSTAINABLE HYDROGEN ENERGY CONSORTIUM CORE PROGRAMME
Engineering and Physical Sciences Research Council
1/07/07 → 30/06/12
Project: Research council
Profiles
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Tim Mays
- Department of Chemical Engineering - Professor
- Institute for Sustainable Energy and the Environment - Director
- Centre for Sustainable and Circular Technologies (CSCT) - Co-Director
- Water Innovation and Research Centre (WIRC)
- Institute for Policy Research (IPR)
- Institute for Sustainability
- Centre for Sustainable Energy Systems (SES)
- EPSRC Centre for Doctoral Training in Advanced Automotive Propulsion Systems (AAPS CDT)
- Institute for Advanced Automotive Propulsion Systems (IAAPS)
Person: Research & Teaching, Core staff, Affiliate staff
Datasets
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Data for cryocharging and cryokinetics analysis of hydrogen storage in MIL-101 (Cr) and AX-21
Bimbo, N. (Creator), Ting, V. (Creator), Mays, T. (Data Curator), Xu, W. (Researcher) & Sharpe, J. (Researcher), University of Bath, 8 Jun 2015
DOI: 10.15125/BATH-00099
Dataset