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

The contactor comprises two arborescent networks of pipes (A, B) tangled together by interleaving respective pipes. Each arborescent networks consists of successive subdivisions of principal pipe (CP(A), CP(B)) each leading to a higher number of smaller pipes to generate a multi-scale pipes. The contactor is present in the form of alternating subdivision stages (ES 1-ES 4) of pipes forming different networks, and interlacing stages (EL 1-EL 3) of the pipes. The structure of each network of pipes is obtained by iterative application of principal pipe of basic operations. The contactor comprises two arborescent networks of pipes (A, B) tangled together by interleaving respective pipes. Each arborescent networks consists of successive subdivisions of principal pipe (CP(A), CP(B)) each leading to a higher number of smaller pipes to generate a multi-scale pipes. The contactor is present in the form of alternating subdivision stages (ES 1-ES 4) of pipes forming different networks, and interlacing stages (EL 1-EL 3) of the pipes. The structure of each network of pipes is obtained by iterative application of principal pipe of basic operations. The pipes of two networks are in thermal contact between each other. The entanglement between the two pipes is achieved by symmetrically angled sections of the pipes, and between the two adjacent pipes is achieved by continuous rotation of a wall separating the pipes, where the wall is helical in shape. The contactor includes a first and a second supply contactor (S 2) connected in series with opposed orientation. The second supply contactor is: configured to recombine subdivided fluids interleaved between pipes by the first supply contactor (S 1); and does not mix the fluid in different network constituting the first supply contactor or allows homogenization of fluid flow flowing within different pipes thus compensating for differences in fluid loss between different paths through the network. The first and second supply contactors are separated by a section comprising parallel and non-interleaved channels and by a mixing section in which the pipes belonging to the different networks are merged. The mixing section is constituted of outlined pipes to promote mixing of fluids circulating in the section. An independent claim is included for a stereo lithographic process for fabricating the contactor.

Contactor for thermal transfer, mixing and chemical reaction operations between fluids, comprises two arborescent networks of pipes tangled together by interleaving respective pipes, where each networks comprise successive subdivisions

Recycle and Flow-Reversal Schemes in Nonlinear Production-Scale Chromatography

Perturbative solutions for non-linear fixed-bed adsorption—II. Approximate analytical expressions for the dynamics of micro-columns

PROCEDE POUR SEPARER EN CONTINU LES CONSTITUANTS D'UN MELANGE CARACTERISE EN CE QU'IL CONSISTE A INTRODUIRE LE MELANGE GAZEUX DANS UNE ENCEINTE CONTENANT UN ADSORBANT SELECTIF, ET A SOUMETTRE LEDIT MELANGE A UNE SERIE CYCLIQUE D'ETAPES CHAUDES ET FROIDES PROVOQUEES PAR DE BRUSQUES VARIATIONS DE TEMPERATURES ENTRE UNE TEMPERATURE T DITE TEMPERATURE HAUTE ET UNE TEMPERATURE T DITE TEMPERATURE FROIDE AFIN DE CREER DANS LES ETAPES FROIDES TROIS ZONES SUCCESSIVES DISTINCTES SE DEPLACANT DANS LE SENS DE L'ECOULEMENT A DES VITESSES DIFFERENTES: UNE ZONE DE PETITE VITESSE DE PROPAGATION COMPRENANT UN FRONT DE SORPTION DANS LEQUEL LA CONCENTRATION DU GAZ EN COMPOSANTS LES PLUS ADSORBABLES DIMINUE; -UNE ZONE DITE "ONDE THERMIQUE" PROVOQUEE A DES TEMPS DETERMINES PAR LE REFROIDISSEMENT BRUSQUE DU MELANGE DE CHARGE. -UNE ZONE DE DESORPTION OU LE MELANGE S'ENRICHIT DANS LES COMPOSANTS LES PLUS ADSORBABLES.

Daniel Tondeur

Papers

Contactor for thermal transfer, mixing and chemical reaction operations between fluids, comprises two arborescent networks of pipes tangled together by interleaving respective pipes, where each networks comprise successive subdivisions

Recycle and Flow-Reversal Schemes in Nonlinear Production-Scale Chromatography

Perturbative solutions for non-linear fixed-bed adsorption—II. Approximate analytical expressions for the dynamics of micro-columns

Procede de separation ou de purification de melanges a l'aide d'un solide adsorbant