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François-xavier Coudert - One of the best experts on this subject based on the ideXlab platform.
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A pressure-amplifying framework material with negative Gas Adsorption transitions
Nature, 2016Co-Authors: Simon Krause, Dirk Wallacher, V. Bon, Ulrich Stoeck, Stefan Zander, Renjith S Pillai, Irena Senkovska, Daniel M. Többens, Guillaume Maurin, François-xavier CoudertAbstract:Adsorption-based phenomena are important in Gas separations1, 2, such as the treatment of greenhouse-Gas3 and toxic-Gas4 pollutants, and in water-Adsorption-based heat pumps5 for solar cooling systems. The ability to tune the pore size, shape and functionality of crystalline porous coordination polymers—or metal–organic frameworks (MOFs)—has made them attractive materials for such Adsorption-based applications3, 6, 7, 8. The flexibility and guest-molecule-dependent response9, 10 of MOFs give rise to unexpected and often desirable Adsorption phenomena11, 12, 13, 14. Common to all isothermal Gas Adsorption phenomena, however, is increased Gas uptake with increased pressure. Here we report Adsorption transitions in the isotherms of a MOF (DUT-49) that exhibits a negative Gas Adsorption; that is, spontaneous desorption of Gas (methane and n-butane) occurs during pressure increase in a defined temperature and pressure range. A combination of in situ powder X-ray diffraction, Gas Adsorption experiments and simulations shows that this Adsorption behaviour is controlled by a sudden hysteretic structural deformation and pore contraction of the MOF, which releases guest molecules. These findings may enable technologies using frameworks capable of negative Gas Adsorption for pressure amplification in micro- and macroscopic system engineering. Negative Gas Adsorption extends the series of counterintuitive phenomena such as negative thermal expansion15, 16 and negative refractive indices17 and may be interpreted as an adsorptive analogue of force-amplifying negative compressibility transitions proposed for metamaterials18
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Origins of Negative Gas Adsorption
Chem, 2016Co-Authors: Jack D. Evans, Lydéric Bocquet, François-xavier CoudertAbstract:Summary Negative Gas Adsorption by a porous crystalline solid, DUT-49, observed by spontaneous desorption of Gas during a pressure increase raises fundamental questions on the physical origin of this puzzling behavior. Importantly, a framework that can transform a large amount of strain into pressure has many possible technological applications. To address this question, we studied the mechanics and thermodynamics of DUT-49 at both the molecular unit and framework scales by applying quantum density functional theory and extensive classical molecular-dynamics simulations. We demonstrate that negative Gas Adsorption originates from molecular buckling of the organic structural unit and thus allows a colossal framework transformation. Methane Adsorption is subsequently shown to activate this transition, in full agreement with experimental observations. The molecular insight presented here unveils the mechanics and thermodynamics responsible for negative Gas Adsorption and provides unparalleled understanding to aid the discovery of new examples of similarly responsive porous metamaterials.
Krzysztof Nieszporek - One of the best experts on this subject based on the ideXlab platform.
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Application of the vacancy solution theory to describe the enthalpic effects accompanying mixed-Gas Adsorption.
Langmuir : the ACS journal of surfaces and colloids, 2006Co-Authors: Krzysztof NieszporekAbstract:The possibility of utilizing vacancy solution theory (VST) to study the enthalpic effects accompanying mixed-Gas Adsorption equilibria is presented. Besides heterogeneity, the interaction effects by using the regular adsorbed solution, Flory-Huggins, and Wilson models of nonideality in the adsorbed phase are taken into account. To predict Adsorption phase diagrams and calorimetric effects in the mixed-Gas Adsorption system, only a knowledge of the single-Gas Adsorption isotherms and accompanying calorimetric effects is required. The possibility of simplification of the obtained theoretical expressions is shown. The obtained agreement between theory and experiment is very satisfactory.
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The application of NIAS approach to describe enthalpic effects accompanying mixed-Gas Adsorption
Applied Surface Science, 2003Co-Authors: Krzysztof NieszporekAbstract:Abstract The possibilities of the non-ideal adsorbed solution (NIAS) approach to study enthalpic effects accompanying mixed-Gas Adsorption equilibria is presented. Besides heterogeneity the interaction effects are taken into account. The obtained theoretical expressions for predicting isosteric heats of Adsorption in the Gas mixture are relatively simple and accurate. To predict phase diagrams and calorimetric effects in the mixed-Gas Adsorption only the knowledge of single-Gas Adsorption isotherms and accompanying calorimetric effects is required.
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On the Correct Use of the Dubinin-Astakhov Equation to Study the Mixed-Gas Adsorption Equilibria
Adsorption, 2002Co-Authors: Krzysztof NieszporekAbstract:This paper presents the possibilities of Integral Equation (IE) approach to study the mixed-Gas Adsorption equilibria. As a result, the generalizations of Dubinin-Astakhov equation for the case of mixed-Gas Adsorption are presented. These new equations are examined using a few Adsorption systems recently published in literature.
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On the theoretical origin and applicability of the potential theory approach to predict mixed-Gas Adsorption on solid surfaces from single-Gas Adsorption isotherms
Chemical Engineering Science, 1995Co-Authors: Władysław Rudziński, Krzysztof Nieszporek, Hee Moon, Hyun-ku RheeAbstract:Abstract A rigorous theoretical development of the Potential Theory Approach for predicting mixed-Gas Adsorption on solids from single-Gas Adsorption isotherms is given. That approach requires very simple computer calculations making it very attractive for process design and control in industrial applications of mixed-Gas Adsorption on solids. It is shown that the “coalescence” operation can be treated as a purely numerical operation not involving the knowledge or assumptions about some physical quantities the meaning of which is not clear. However, it is also shown that the traditional coalescence operation is not the best way to elucidate the values of the parameters which are necessary to predict mixed-Gas Adsorption equilibria. A more effective way to determine the values of these parameters better, based on a theoretical analysis of single-Gas Adsorption isotherms, is proposed.
Simon Krause - One of the best experts on this subject based on the ideXlab platform.
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A pressure-amplifying framework material with negative Gas Adsorption transitions
Nature, 2016Co-Authors: Simon Krause, Dirk Wallacher, V. Bon, Ulrich Stoeck, Stefan Zander, Renjith S Pillai, Irena Senkovska, Daniel M. Többens, Guillaume Maurin, François-xavier CoudertAbstract:Adsorption-based phenomena are important in Gas separations1, 2, such as the treatment of greenhouse-Gas3 and toxic-Gas4 pollutants, and in water-Adsorption-based heat pumps5 for solar cooling systems. The ability to tune the pore size, shape and functionality of crystalline porous coordination polymers—or metal–organic frameworks (MOFs)—has made them attractive materials for such Adsorption-based applications3, 6, 7, 8. The flexibility and guest-molecule-dependent response9, 10 of MOFs give rise to unexpected and often desirable Adsorption phenomena11, 12, 13, 14. Common to all isothermal Gas Adsorption phenomena, however, is increased Gas uptake with increased pressure. Here we report Adsorption transitions in the isotherms of a MOF (DUT-49) that exhibits a negative Gas Adsorption; that is, spontaneous desorption of Gas (methane and n-butane) occurs during pressure increase in a defined temperature and pressure range. A combination of in situ powder X-ray diffraction, Gas Adsorption experiments and simulations shows that this Adsorption behaviour is controlled by a sudden hysteretic structural deformation and pore contraction of the MOF, which releases guest molecules. These findings may enable technologies using frameworks capable of negative Gas Adsorption for pressure amplification in micro- and macroscopic system engineering. Negative Gas Adsorption extends the series of counterintuitive phenomena such as negative thermal expansion15, 16 and negative refractive indices17 and may be interpreted as an adsorptive analogue of force-amplifying negative compressibility transitions proposed for metamaterials18
Jorg J Schneider - One of the best experts on this subject based on the ideXlab platform.
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Gas Adsorption studies of co2 and n2 in spatially aligned double walled carbon nanotube arrays
Carbon, 2013Co-Authors: Deepu J Babu, Marcus Lange, Gennady Cherkashinin, Alexander Issanin, Reiner Staudt, Jorg J SchneiderAbstract:Gas Adsorption studies (CO2 and N2) over a wide pressure range on vertically, highly aligned dense double-walled carbon nanotube arrays of high purity and high specific surface area are reported. At high pressures, the Adsorption capacity of these materials was found to be comparable to those of metal organic frameworks and mesoporous molecular sieves. These highly aligned CNT arrays were chemically modified by treating with oxygen plasma and structurally modified by decreasing the diameter of individual carbon nanotubes. Oxygen plasma treatment led to grafting of a large number of C–O functional groups onto the CNT surface, which further increased the Gas Adsorption capacity. It was found that Gas Adsorption is dependent on tube diameter and increases with decrease of the individual CNT diameter in the CNT bundles. As results of our studies we have found that at lower pressure regimes, plasma functionalized carbon nanotubes exhibit better Adsorption characteristics whereas at higher pressures, lower diameter carbon nanotube structures exhibited better Gas Adsorption characteristics.
Mohamad Hassan - One of the best experts on this subject based on the ideXlab platform.
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Comparison of Temperature-Dependent Gas Adsorption Models and Their Application to Shale Gas Reservoirs
Energy & Fuels, 2018Co-Authors: John Senam Fianu, Jebraeel Gholinezhad, Mohamad HassanAbstract:Significant quantities of Gas are adsorbed onto the rock matrix in shale Gas reservoirs. Accounting for this adsorbed Gas in reservoir calculations is key for realistic estimations of Gas in place and overall Gas production, and later as a target for enhanced Gas recovery methods like thermal stimulation. The classical Langmuir isotherm fails to represent Gas Adsorption at multiple temperatures, thereby making its application in thermal stimulation strategies limited. In this work, several temperature-dependent Gas Adsorption models were reviewed and grouped further into both temperature-dependent and -independent Langmuir volume. Application of the models to several shale Gas data sets obtained from different regions shows minimal differences in the successful prediction of Gas Adsorption using either the temperature-dependent or -independent Langmuir volume models. However, caution is to be exercised in the choice of models for use in numerical simulation studies when extrapolating to temperatures that ...
