Supercritical hydrogen adsorption in nanostructured solids with hydrogen density variation in pores
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Supercritical hydrogen adsorption in nanostructured solids with hydrogen density variation in pores Jessica E. Sharpe • Nuno Bimbo • Valeska P. Ting Andrew D. Burrows • Dongmei Jiang • Timothy J. Mays
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Received: 31 October 2012 / Accepted: 24 January 2013 / Published online: 22 February 2013 Ó Springer Science+Business Media New York 2013
Abstract Experimental excess isotherms for the adsorption of gases in porous solids may be represented by mathematical models that incorporate the total amount of gas within a pore, a quantity which cannot easily be found experimentally but which is important for calculations for many applications, including adsorptive storage. A model that is currently used for hydrogen adsorption in porous solids has been improved to include a more realistic density profile of the gas within the pore, and allows calculation of the total amount of adsorbent. A comparison has been made between different Type I isotherm equations embedded in the model, by examining the quality of the fits to hydrogen isotherms for six different nanoporous materials. A new Type I isotherm equation which has not previously been reported in the literature, the Unilanb equation, has been derived and has also been included in this comparison study. These results indicate that while some Type I isotherm equations fit certain types of materials better than others, the To´th equation produces the best overall quality of fit and also provides realistic parameter Electronic supplementary material The online version of this article (doi:10.1007/s10450-013-9487-6) contains supplementary material, which is available to authorized users. J. E. Sharpe Department of Chemical Engineering, EPSRC Doctoral Training Centre, Centre for Sustainable Chemical Technologies, University of Bath, Bath BA27AY, UK N. Bimbo V. P. Ting T. J. Mays (&) Department of Chemical Engineering, University of Bath, Bath BA27AY, UK e-mail: [email protected] A. D. Burrows D. Jiang Department of Chemistry, University of Bath, Bath BA2 7AY, UK
values when used to analyse hydrogen sorption data for a model carbon adsorbent. Keywords Hydrogen adsorption Porous solids Isotherm equations List of symbols MOF Metal–organic framework PIM Polymer of intrinsic microporosity mE Excess mass of hydrogen vP Pore volume qB Bulk density mmax Limiting maximum uptake A hA Fractional filling wt % Weight percent P Absolute pressure b Affinity parameter Q Enthalpic factor b0 Pre-exponential factor R Molar gas constant T Absolute temperature bdc Benzene-1,4-dicarboxylate MIL Mate´riaux de l’Institut Lavoisier BET Brunauer, Emmett and Teller mB(A) Bulk hydrogen within the adsorbate mA Absolute uptake mP Total uptake qA Adsorbate density vA Adsorbate volume M Molar mass Z Compressibility factor NIST National Institute of Standards and Technology b(T) To´th affinity parameter c(T) To´th heterogeneity parameter RMSR Root mean square residual
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b1 b2 Q1 Q2 h(P,h) h w b(L) b(S) m(S) b(GF) q b(JF) c(JF) a b m(DA) P0 GCMC
Adsorption (2013) 19:643–652
Minimum valu
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