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Analysis of parameter values in the van der waals and platteeuw theory for methane hydrates using monte carlo molecular simulations / Srikanth Ravipati in Industrial & engineering chemistry research, Vol. 51 N° 27 (Juillet 2012) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 51 N° 27 (Juillet 2012) . - pp. 9419–9426 Titre : Analysis of parameter values in the van der waals and platteeuw theory for methane hydrates using monte carlo molecular simulations Type de document : texte imprimé Auteurs : Srikanth Ravipati, Auteur ; Sudeep N. Punnathanam, Auteur Année de publication : 2012 Article en page(s) : pp. 9419–9426 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Methane  Hydrates Résumé : The van der Waals and Platteuw (vdWP) theory has been successfully used to model the thermodynamics of gas hydrates. However, earlier studies have shown that this could be due to the presence of a large number of adjustable parameters whose values are obtained through regression with experimental data. To test this assertion, we carry out a systematic and rigorous study of the performance of various models of vdWP theory that have been proposed over the years. The hydrate phase equilibrium data used for this study is obtained from Monte Carlo molecular simulations of methane hydrates. The parameters of the vdWP theory are regressed from this equilibrium data and compared with their true values obtained directly from simulations. This comparison reveals that (i) methane–water interactions beyond the first cage and methane–methane interactions make a significant contribution to the partition function and thus cannot be neglected, (ii) the rigorous Monte Carlo integration should be used to evaluate the Langmuir constant instead of the spherical smoothed cell approximation, (iii) the parameter values describing the methane–water interactions cannot be correctly regressed from the equilibrium data using the vdWP theory in its present form, (iv) the regressed empty hydrate property values closely match their true values irrespective of the level of rigor in the theory, and (v) the flexibility of the water lattice forming the hydrate phase needs to be incorporated in the vdWP theory. Since methane is among the simplest of hydrate forming molecules, the conclusions from this study should also hold true for more complicated hydrate guest molecules. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie3004368 [article] Analysis of parameter values in the van der waals and platteeuw theory for methane hydrates using monte carlo molecular simulations [texte imprimé] / Srikanth Ravipati, Auteur ; Sudeep N. Punnathanam, Auteur . - 2012 . - pp. 9419–9426. Industrial chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 51 N° 27 (Juillet 2012) . - pp. 9419–9426 Mots-clés : Methane  Hydrates Résumé : The van der Waals and Platteuw (vdWP) theory has been successfully used to model the thermodynamics of gas hydrates. However, earlier studies have shown that this could be due to the presence of a large number of adjustable parameters whose values are obtained through regression with experimental data. To test this assertion, we carry out a systematic and rigorous study of the performance of various models of vdWP theory that have been proposed over the years. The hydrate phase equilibrium data used for this study is obtained from Monte Carlo molecular simulations of methane hydrates. The parameters of the vdWP theory are regressed from this equilibrium data and compared with their true values obtained directly from simulations. This comparison reveals that (i) methane–water interactions beyond the first cage and methane–methane interactions make a significant contribution to the partition function and thus cannot be neglected, (ii) the rigorous Monte Carlo integration should be used to evaluate the Langmuir constant instead of the spherical smoothed cell approximation, (iii) the parameter values describing the methane–water interactions cannot be correctly regressed from the equilibrium data using the vdWP theory in its present form, (iv) the regressed empty hydrate property values closely match their true values irrespective of the level of rigor in the theory, and (v) the flexibility of the water lattice forming the hydrate phase needs to be incorporated in the vdWP theory. Since methane is among the simplest of hydrate forming molecules, the conclusions from this study should also hold true for more complicated hydrate guest molecules. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie3004368