Documents disponibles écrits par cet auteur

Continuous-molecular targeting for integrated solvent and process design / Andre Bardow in Industrial & engineering chemistry research, Vol. 49 N° 6 (Mars 2010) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 49 N° 6 (Mars 2010) . - pp. 2834–2840 Titre : Continuous-molecular targeting for integrated solvent and process design Type de document : texte imprimé Auteurs : Andre Bardow, Auteur ; Klaas Steur, Auteur ; Joachim Gross, Auteur Année de publication : 2010 Article en page(s) : pp. 2834–2840 Note générale : Idustrial Chemistry Langues : Anglais (eng) Mots-clés : Molecular;  Solvent;  topology;  fluid  theory;  study; Résumé : An integrated design of processes and solvents is a prerequisite for achieving truly optimized solvent-based processes. However, solving the full integrated problem in a single optimization is usually not possible even for a predefined process topology due to the required discrete choices between molecular structures. Current approaches therefore mostly decompose the integrated problem into a process design and a molecular-design subproblem. The interaction between these subproblems is usually limited in practice, and a direct link between process performance and molecular characteristics of the solvent is not achieved. In this work, a novel methodology for the integrated process and molecular design problem is suggested where the discrete molecular decisions in the integrated design problem are circumvented by defining a hypothetical molecule. The approach is building upon a molecular-based thermodynamic model, where the parameters representing a molecule are treated as continuous. These parameters are optimized together with other process parameters, leading to an ideal hypothetical target molecule (represented by a set of parameters) and a corresponding optimized process. Only in a subsequent step, the parameters of the thermodynamic model representing the hypothetical molecule are mapped onto an existing optimal solvent. The method is illustrated for the design of solvents for carbon dioxide capture where the benefits of the integrated design approach are demonstrated. The perturbed-chain-polar-statistical-associating-fluid theory (PCP-SAFT) equation of state is used as a thermodynamic model. The framework introduced is generic in nature and thus applicable beyond the study of solvents to the integrated design of materials and processes in general. Note de contenu : Bibiogr. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901281w [article] Continuous-molecular targeting for integrated solvent and process design [texte imprimé] / Andre Bardow, Auteur ; Klaas Steur, Auteur ; Joachim Gross, Auteur . - 2010 . - pp. 2834–2840. Idustrial Chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 49 N° 6 (Mars 2010) . - pp. 2834–2840 Mots-clés : Molecular;  Solvent;  topology;  fluid  theory;  study; Résumé : An integrated design of processes and solvents is a prerequisite for achieving truly optimized solvent-based processes. However, solving the full integrated problem in a single optimization is usually not possible even for a predefined process topology due to the required discrete choices between molecular structures. Current approaches therefore mostly decompose the integrated problem into a process design and a molecular-design subproblem. The interaction between these subproblems is usually limited in practice, and a direct link between process performance and molecular characteristics of the solvent is not achieved. In this work, a novel methodology for the integrated process and molecular design problem is suggested where the discrete molecular decisions in the integrated design problem are circumvented by defining a hypothetical molecule. The approach is building upon a molecular-based thermodynamic model, where the parameters representing a molecule are treated as continuous. These parameters are optimized together with other process parameters, leading to an ideal hypothetical target molecule (represented by a set of parameters) and a corresponding optimized process. Only in a subsequent step, the parameters of the thermodynamic model representing the hypothetical molecule are mapped onto an existing optimal solvent. The method is illustrated for the design of solvents for carbon dioxide capture where the benefits of the integrated design approach are demonstrated. The perturbed-chain-polar-statistical-associating-fluid theory (PCP-SAFT) equation of state is used as a thermodynamic model. The framework introduced is generic in nature and thus applicable beyond the study of solvents to the integrated design of materials and processes in general. Note de contenu : Bibiogr. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901281w

Multicomponent maxwell−stefan diffusivities at infinite dilution / Xin Liu in Industrial & engineering chemistry research, Vol. 50 N° 8 (Avril 2011) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 50 N° 8 (Avril 2011) . - pp. 4776–4782 Titre : Multicomponent maxwell−stefan diffusivities at infinite dilution Type de document : texte imprimé Auteurs : Xin Liu, Auteur ; Andre Bardow, Auteur ; Thijs J.H. Vlugt, Auteur Année de publication : 2011 Article en page(s) : pp. 4776–4782 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Chemical  processes Résumé : Diffusion plays an important role in (bio)chemical processes. It is usually difficult to obtain Maxwell−Stefan diffusivities from experiments as well as molecular simulation. Therefore, predictive models based on easily measurable quantities are highly desired. The Vignes equation is commonly used to describe the concentration dependence of Maxwell−Stefan diffusivities. In mixtures containing at least three components, the generalized Vignes equation requires the value of the quantity Đijxk→1, which describes the friction between components i and j when both are infinitely diluted in component k. Over the past decades, several empirical models were proposed for estimating Đijxk→1, and all of these are lacking a sound theoretical basis. In this study, we show that Đijxk→1 actually exists (i.e., its value does not depend on the molar ratio xi/xj), and we derive an analytical expression for Đijxk→1 that is based on the linear response theory and the Onsager relations. We find that Đijxk→1 can be expressed in terms of binary and pure-component self-diffusivities and integrals over velocity cross-correlation functions. By neglecting the latter terms, we obtain a convenient predictive model for Đijxk→1. Molecular dynamics simulations are used to validate the assumptions made in this model. The following test systems are considered: a ternary system consisting of particles interacting using Weeks−Chandler−Andersen (WCA) interactions and the ternary systems n-hexane−cyclohexane−toluene and ethanol−methanol−water. Our results show that (1) for the WCA system, as well as the n-hexane−cyclohexane−toluene system, neglecting the integrals over velocity cross-correlation functions results in accurate predictions for Đijxk→1; (2) for the WCA system, our model prediction is superior, compared to the existing models for Đijxk→1; (3) in the ethanol−methanol−water system, the integrals over velocity cross-correlation functions cannot be neglected, because of the presence of hydrogen bonds (models for predicting Đijxk→1 in this system will require detailed information on the collective motion of molecules); and (4) our model may provide an explanation why the Maxwell−Stefan diffusivity describing the friction between adsorbed components in a porous material is usually very large. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie102515w [article] Multicomponent maxwell−stefan diffusivities at infinite dilution [texte imprimé] / Xin Liu, Auteur ; Andre Bardow, Auteur ; Thijs J.H. Vlugt, Auteur . - 2011 . - pp. 4776–4782. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 50 N° 8 (Avril 2011) . - pp. 4776–4782 Mots-clés : Chemical  processes Résumé : Diffusion plays an important role in (bio)chemical processes. It is usually difficult to obtain Maxwell−Stefan diffusivities from experiments as well as molecular simulation. Therefore, predictive models based on easily measurable quantities are highly desired. The Vignes equation is commonly used to describe the concentration dependence of Maxwell−Stefan diffusivities. In mixtures containing at least three components, the generalized Vignes equation requires the value of the quantity Đijxk→1, which describes the friction between components i and j when both are infinitely diluted in component k. Over the past decades, several empirical models were proposed for estimating Đijxk→1, and all of these are lacking a sound theoretical basis. In this study, we show that Đijxk→1 actually exists (i.e., its value does not depend on the molar ratio xi/xj), and we derive an analytical expression for Đijxk→1 that is based on the linear response theory and the Onsager relations. We find that Đijxk→1 can be expressed in terms of binary and pure-component self-diffusivities and integrals over velocity cross-correlation functions. By neglecting the latter terms, we obtain a convenient predictive model for Đijxk→1. Molecular dynamics simulations are used to validate the assumptions made in this model. The following test systems are considered: a ternary system consisting of particles interacting using Weeks−Chandler−Andersen (WCA) interactions and the ternary systems n-hexane−cyclohexane−toluene and ethanol−methanol−water. Our results show that (1) for the WCA system, as well as the n-hexane−cyclohexane−toluene system, neglecting the integrals over velocity cross-correlation functions results in accurate predictions for Đijxk→1; (2) for the WCA system, our model prediction is superior, compared to the existing models for Đijxk→1; (3) in the ethanol−methanol−water system, the integrals over velocity cross-correlation functions cannot be neglected, because of the presence of hydrogen bonds (models for predicting Đijxk→1 in this system will require detailed information on the collective motion of molecules); and (4) our model may provide an explanation why the Maxwell−Stefan diffusivity describing the friction between adsorbed components in a porous material is usually very large. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie102515w

Predictive darken equation for maxwell-stefan diffusivities in multicomponent mixtures / Xin Liu in Industrial & engineering chemistry research, Vol. 50 N° 17 (Septembre 2011) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 50 N° 17 (Septembre 2011) . - pp. 10350-10358 Titre : Predictive darken equation for maxwell-stefan diffusivities in multicomponent mixtures Type de document : texte imprimé Auteurs : Xin Liu, Auteur ; Thijs J.H. Vlugt, Auteur ; Andre Bardow, Auteur Année de publication : 2011 Article en page(s) : pp. 10350-10358 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Multicomponent  mixture  Diffusion  coefficient Résumé : This Article presents the derivation and validation of a rigorous model for the prediction of multicomponent Maxwell-Stefan (MS) diffusion coefficients. The MS theory provides a sound framework for modeling mass transport in gases and liquids. Unfortunately, MS diffusivities are concentration dependent, and this needs to be taken into account in practical applications. There is therefore a considerable interest in models describing the concentration dependence ofMS diffusivities. While current practice employs empirical models for this purpose, recent work on molecular simulations favor the physically based Darken equation. The Darken equation, however, is limited to binary mixtures and is not predictive. In this study, a multicomponent Darken model for MS diffusivities is derived from linear response theory and the Onsager relations. In addition, a predictive model for the required self-diffusivities in the mixture is proposed, leading to the predictive Darken-LBV model. We compare our novel model to the existing generalized Vignes equation and the generalized Darken equation using molecular dynamics (MD) simulation. Two systems are considered: (1) ternary and quaternary systems in which particles are interacting using the Weeks-Chandler-Andersen (WCA) potential; (2) the ternary system n-hexane-cyclohexane-toluene. Our results show that, in all studied systems, the novel predictive Darken-LBV equation describes the concentration dependence better than the existing models. The physically based Darken-LBV model provides a sound and robust framework for prediction ofMS diffusion coefficients in multicomponent mixtures. DEWEY : 660 ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=24483681 [article] Predictive darken equation for maxwell-stefan diffusivities in multicomponent mixtures [texte imprimé] / Xin Liu, Auteur ; Thijs J.H. Vlugt, Auteur ; Andre Bardow, Auteur . - 2011 . - pp. 10350-10358. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 50 N° 17 (Septembre 2011) . - pp. 10350-10358 Mots-clés : Multicomponent  mixture  Diffusion  coefficient Résumé : This Article presents the derivation and validation of a rigorous model for the prediction of multicomponent Maxwell-Stefan (MS) diffusion coefficients. The MS theory provides a sound framework for modeling mass transport in gases and liquids. Unfortunately, MS diffusivities are concentration dependent, and this needs to be taken into account in practical applications. There is therefore a considerable interest in models describing the concentration dependence ofMS diffusivities. While current practice employs empirical models for this purpose, recent work on molecular simulations favor the physically based Darken equation. The Darken equation, however, is limited to binary mixtures and is not predictive. In this study, a multicomponent Darken model for MS diffusivities is derived from linear response theory and the Onsager relations. In addition, a predictive model for the required self-diffusivities in the mixture is proposed, leading to the predictive Darken-LBV model. We compare our novel model to the existing generalized Vignes equation and the generalized Darken equation using molecular dynamics (MD) simulation. Two systems are considered: (1) ternary and quaternary systems in which particles are interacting using the Weeks-Chandler-Andersen (WCA) potential; (2) the ternary system n-hexane-cyclohexane-toluene. Our results show that, in all studied systems, the novel predictive Darken-LBV equation describes the concentration dependence better than the existing models. The physically based Darken-LBV model provides a sound and robust framework for prediction ofMS diffusion coefficients in multicomponent mixtures. DEWEY : 660 ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=24483681