Pore size determination in modified micro- and mesoporous materials. Pitfalls and limitations in gas adsorption data analysis

Entropy generation minimization (finite time thermodynamics, or thermodynamic optimization) is the method that combines into simple models the most basic concepts of heat transfer, fluid mechanics, and thermodynamics. These simple models are used in the optimization of real (irreversible) devices and processes, subject to finite‐size and finite‐time constraints. The review traces the development and adoption of the method in several sectors of mainstream thermal engineering and science: cryogenics, heat transfer, education, storage systems, solar power plants, nuclear and fossil power plants, and refrigerators. Emphasis is placed on the fundamental and technological importance of the optimization method and its results, the pedagogical merits of the method, and the chronological development of the field.

Entropy generation minimization: The new thermodynamics of finite-size devices and finite-time processes

Preface. 1. Introductory Remarks. 2. Fundamental Factors for Designing Adsorbent. 3. Sorbent Selection: Equilibrium Isotherms, Diffusion, Cyclic Processes, and Sorbent Selection Criteria. 4. Pore Size Distribution. 5. Activated Carbon. 6. Silica Gel, MCM, and Activated Alumina. 7. Zeolites and Molecular Sieves. 8. &pi -Complexation Sorbents and Applications. 9. Carbon Nanotubes, Pillared Clays, and Polymeric Resins. 10. Sorbents for Applications. Author Index. Subject Index.

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Adsorbents: Fundamentals and Applications

A pressure swing adsorption cycle comprised of blowdown, purge, pressurization, feed, pressure equalization and rinse steps provided recovery from an atmospheric air feed, essentially dry and free of carbon dioxide, of a high yield of high purity nitrogen gas and a high yield of a product gas rich in oxygen as well as recovery of a residual feed byproduct gas for recycle with the air feed.

Pressure swing adsorption

Two flexible metal-organic frameworks are presented as solid adsorbents for methane that undergo reversible phase transitions at specific methane pressures, enabling greater storage capacities of usable methane than have been achieved previously, while also providing internal heat management of the system. Natural gas — methane — is a clean and cheap fuel but its usefulness in transport applications is limited by storage problems, given its low energy density per unit volume under ambient conditions compared with petrol or diesel. One way of increasing methane storage capacity is to use tanks containing porous materials, such as metal–organic frameworks, as a storage medium. However, for every methane molecule adsorbed and desorbed there is an associated thermal fluctuation that could cause overheating or reduce storage efficiency if left unchecked. Here Jeffrey Long and colleagues describe two flexible metal–organic frameworks that undergo reversible phase transitions at specific methane pressures, enabling greater storage capacities of usable methane than have been achieved previously, while also providing internal heat management of the system. As a cleaner, cheaper, and more globally evenly distributed fuel, natural gas has considerable environmental, economic, and political advantages over petroleum as a source of energy for the transportation sector1,2. Despite these benefits, its low volumetric energy density at ambient temperature and pressure presents substantial challenges, particularly for light-duty vehicles with little space available for on-board fuel storage3. Adsorbed natural gas systems have the potential to store high densities of methane (CH4, the principal component of natural gas) within a porous material at ambient temperature and moderate pressures4. Although activated carbons, zeolites, and metal–organic frameworks have been investigated extensively for CH4 storage5,6,7,8, there are practical challenges involved in designing systems with high capacities and in managing the thermal fluctuations associated with adsorbing and desorbing gas from the adsorbent. Here, we use a reversible phase transition in a metal–organic framework to maximize the deliverable capacity of CH4 while also providing internal heat management during adsorption and desorption. In particular, the flexible compounds Fe(bdp) and Co(bdp) (bdp2− = 1,4-benzenedipyrazolate) are shown to undergo a structural phase transition in response to specific CH4 pressures, resulting in adsorption and desorption isotherms that feature a sharp ‘step’. Such behaviour enables greater storage capacities than have been achieved for classical adsorbents9, while also reducing the amount of heat released during adsorption and the impact of cooling during desorption. The pressure and energy associated with the phase transition can be tuned either chemically or by application of mechanical pressure.

Methane storage in flexible metal–organic frameworks with intrinsic thermal management

RESEARCH ARTICLE Modeling and Simulation of Pressure Equalization Step Between a Packed Bed and an Empty Tank in Pressure Swing Adsorption Cycles Mohamed Hachemi Chahbani, R. Talmoudi, Amna Abdel Jaoued and D. Tondeur Institut Supérieur des Sciences Appliquées et de Technologie de Gabès, Université de Gabès, Rue Omar Ibn Elkhattab, Zrig, Tunisia Laboratoire Génie des procédés et systèmes industriels (LR11ES54), Université de Gabès, Rue Omar Ibn Elkhattab, Zrig, Gabès 6029, Tunisia Ecole Nationale d'Ingénieurs de Gabès, Université de Gabès, Rue Omar Ibn Elkhattab, Zrig, Gabès 6029, Tunisia Laboratoire Réactions et Génie des Procédés, CNRS et Université de Lorraine, ENSIC, 1 Rue Grandville54000 Nancy France

Pressure equalization step between a packed bed and an empty tank in Pressure Swing Adsorption cycles

Mise au point sur les lois de l'électrophorèse. Extension de la théorie de l'interface mobile, par analogie mathématique avec la chromatographie

Donnan partition parametric pumping. Concentration and dilution effects in ion exchange parametric pumping

Thermodynamics aspects of capillary flows

The feasibility of mono- and di-branched paraffins separation on silicalite was evaluated by performing cyclic breakthrough experiments in liquid phase with mixtures of 2-methylpentane (2MP), 3-methylpentane (3MP), 2,3-dimethylbutane (23DMB), and 2,2-dimethylbutane (22DMB). For mixtures of the faster diffusing species (2MP, 3MP, and 23DMB), cyclic steady state is obtained from the first cycle. On the other hand, when the slow diffusing species 22DMB is involved, a slow accumulation occurs from cycle to cycle, yielding a change of the breakthrough curves for all the species. Using a diffusion model especially adapted to adsorbent saturation loading, the kinetic and thermodynamic parameters of 22DMB were estimated. Influence of the cycling conditions on the separation performance were finally studied by simulation

Daniel Tondeur

Papers

Pressure equalization step between a packed bed and an empty tank in Pressure Swing Adsorption cycles

Mise au point sur les lois de l'électrophorèse. Extension de la théorie de l'interface mobile, par analogie mathématique avec la chromatographie

Donnan partition parametric pumping. Concentration and dilution effects in ion exchange parametric pumping

Thermodynamics aspects of capillary flows

Influence of slow diffusing species on mixture diffusion of hexane isomers in silicalite: Characterization by a new cyclic method