Investigating the validity of the knudsen prescription for diffusivities in a mesoporous covalent organic framework / Rajamani Krishna in Industrial & engineering chemistry research, Vol. 50 N° 11 (Juin 2011)  

Public ISBD [article]  inIndustrial & engineering chemistry research > Vol. 50 N° 11 (Juin 2011) . - pp. 7083-7087 Titre : Investigating the validity of the knudsen prescription for diffusivities in a mesoporous covalent organic framework Type de document : texte imprimé Auteurs : Rajamani Krishna, Auteur ; Jasper M. Van Baten, Auteur Année de publication : 2011 Article en page(s) : pp. 7083-7087 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Diffusion coefficient Résumé : Molecular dynamics (MD) simolations were performed to determine the self-diffusivity (Di,self) and the Mazwell―Stefan diffusivity (Di) of hydrogen, argon, carbon dioxide, methane, ethane, propane, n-butane, n-pentane, and n-hexane in BTP-COF, which is a covalent organic framework (COF) that has one-dimensional 3.4-nm-sized channels. The MD simulations show that the zero-loading diffusivity (Đi(0)) is consistently lower, by up to a factor of 10, than the Knudsen diffusivity (D¡,Kn) values. The ratio Đi(0)/Di,Kn is found to correlate with the isosteric heat of adsorption, which, in turn, is a reflection of the binding energy for adsorption on the pore walls: the stronger the binding energy, the lower the ratio Ði(0)/Di,Kn. The diffusion selectivity, which is defined by the ratio D1,self/ D2,self for binary mixtures, was determined to be significantly different from the Knudsen selectivity (M2/M1) 1/2, where M¡ is the molar mass of species i. For mixtures in which component 2 is more strongly adsorbed than component 1, the expression (D1,self/D2,self)/ (M2/M1)1/2 has values in the range of 1―10; the departures from the Knudsen selectivity increased with increasing differences in adsorption strengths of the constituent species. The results of this study have implications in the modeling of diffusion within mesoporous structures, such as MCM-41 and SBA-15. DEWEY : 660 ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=24199928 [article] Investigating the validity of the knudsen prescription for diffusivities in a mesoporous covalent organic framework [texte imprimé] / Rajamani Krishna, Auteur ; Jasper M. Van Baten, Auteur . - 2011 . - pp. 7083-7087. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 50 N° 11 (Juin 2011) . - pp. 7083-7087 Mots-clés : Diffusion coefficient Résumé : Molecular dynamics (MD) simolations were performed to determine the self-diffusivity (Di,self) and the Mazwell―Stefan diffusivity (Di) of hydrogen, argon, carbon dioxide, methane, ethane, propane, n-butane, n-pentane, and n-hexane in BTP-COF, which is a covalent organic framework (COF) that has one-dimensional 3.4-nm-sized channels. The MD simulations show that the zero-loading diffusivity (Đi(0)) is consistently lower, by up to a factor of 10, than the Knudsen diffusivity (D¡,Kn) values. The ratio Đi(0)/Di,Kn is found to correlate with the isosteric heat of adsorption, which, in turn, is a reflection of the binding energy for adsorption on the pore walls: the stronger the binding energy, the lower the ratio Ði(0)/Di,Kn. The diffusion selectivity, which is defined by the ratio D1,self/ D2,self for binary mixtures, was determined to be significantly different from the Knudsen selectivity (M2/M1) 1/2, where M¡ is the molar mass of species i. For mixtures in which component 2 is more strongly adsorbed than component 1, the expression (D1,self/D2,self)/ (M2/M1)1/2 has values in the range of 1―10; the departures from the Knudsen selectivity increased with increasing differences in adsorption strengths of the constituent species. The results of this study have implications in the modeling of diffusion within mesoporous structures, such as MCM-41 and SBA-15. DEWEY : 660 ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=24199928

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