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

Dans un dispositif de contact ou de separation comprenant une aire de transfert donnee et effectuant un transfert specifie, l'entropie totale produite est minimale lorsque la vitesse locale de production d'entropie est uniformement repartie (equiseparee) le long des variables spatiales et/ou temporelles. Cette propriete est demontree pour les conditions de thermodynamique de non-equilibre classique: relations lineaires flux-force et relations de reciprocite d'Onsager. On montre que les procedes «equisepares» sont optimaux au sens economique, c'est-a-dire qu'ils correspondent au minimum de quelque fonction de cout

Equipartition of entropy production. An optimality criterion for transfer and separation processes

I. Characterization of Adsorbents and Tthermodynamics of Adsorption.- Characterization of adsorbents.- Theories of adsorption in micropores.- The statistical thermodynamic approach to the correlation of equilibrium data.- A two-patch heterogeneous model with surface phase transition for benzene adsorption on silicalite.- Interpretation of low temperature gas adsorption and desorption using stochastic pore networks.- Adsorption of n-hexane and 3-methylpentane on zeolites Y and ZSM 20.- II. Kinetics of Adsorption and Fixed-Bed Processes.- Adsorption kinetics.- Dynamics of fixed-bed adsorbers. Isothermal adsorption of single components.- Asymptotic fixed-bed behavior: proportionate and constant patterns.- Pore scale hydrodynamics.- Separation processes based on electrosorption phenomena.- Adsorptive reactors.- Design aspects of fixed-bed adsorption processes.- Numerical methods for the solution of adsorption models.- III. Cyclic Processes and Simulated Moving Beds.- Gas separation by pressure swing adsorption using carbon molecular sieves.- Pressure swing adsorption technology.- Modeling and simulation of rate induced PSA separations.- Thermal swing adsorption.- On countercurrent adsorption separation processes.- Sorbex: continuing innovation in liquid phase adsorption.- IV. Applications in Biotechnology and Environmental Engineering.- The use of granular activated carbon for potable water treatment as an example of liquid phase applications of activated carbon.- Breakthrough time of organic vapours in activated carbon filters as a function of the air flow pattern.- Continuous adsorption in biotechnology.- Continuous chromatographic processes.- Biochemical reaction and separation in chromatographic columns.- Some factors involved in scale-up of industrial biotechnological adsorption processes.- Development of physical and mathematical modelling for scale-up of batch stirred tank and packed-bed column adsorption and chromatographic units.- Optimisation of adsorption techniques for the purification of biomolecules.- Gel filtration chromatography.- Adsorption chromatography for protein purification.- List of Lecturers and Participants.

Daniel Tondeur

Papers

Equipartition of entropy production. An optimality criterion for transfer and separation processes

Adsorption, science and technology

Design and scaling laws of ramified fluid distributors by the constructal approach

Dynamics of natural gas adsorption storage systems employing activated carbon

Multicomponent Ion Exchange in Fixed Beds. General Properties of Equilibrium Systems