There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Kenji Sumida, David L. Rogow, Jarad A. Mason, Thomas M. McDonald, Eric D. Bloch, Zoey R. Herm, Tae-Hyun Bae, Jeffrey R. Long

Carbon Dioxide Capture in Metal–Organic Frameworks

Application of low-cost adsorbents for dye removal – A review

Since the time of the industrial revolution, the atmospheric CO(2) concentration has risen by nearly 35 % to its current level of 383 ppm. The increased carbon dioxide concentration in the atmosphere has been suggested to be a leading contributor to global climate change. To slow the increase, reductions in anthropogenic CO(2) emissions are necessary. Large emission point sources, such as fossil-fuel-based power generation facilities, are the first targets for these reductions. A benchmark, mature technology for the separation of dilute CO(2) from gas streams is via absorption with aqueous amines. However, the use of solid adsorbents is now being widely considered as an alternative, potentially less-energy-intensive separation technology. This Review describes the CO(2) adsorption behavior of several different classes of solid carbon dioxide adsorbents, including zeolites, activated carbons, calcium oxides, hydrotalcites, organic-inorganic hybrids, and metal-organic frameworks. These adsorbents are evaluated in terms of their equilibrium CO(2) capacities as well as other important parameters such as adsorption-desorption kinetics, operating windows, stability, and regenerability. The scope of currently available CO(2) adsorbents and their critical properties that will ultimately affect their incorporation into large-scale separation processes is presented.

Adsorbent Materials for Carbon Dioxide Capture from Large Anthropogenic Point Sources

https://persianmof.weebly.com/uploads/4/8/8/3/48832931/chem._rev._2014,_114,_10575.pdf

Water stability and adsorption in metal-organic frameworks.

A frequency response method using concentration variation is developed theoretically and experimentally and applied to investigate mixture diffusion in nanoporous adsorbents. The method is based on periodically time-varying species feed concentrations with a constant total molar inlet flow rate. It can be used without the need of a carrier gas. A mathematical model is formulated considering nanopore diffusion, surface barrier resistance, external film resistance, and axial dispersion. The related analytical solutions for frequency response are derived. For nanopore diffusion, a theory for nonconstant mixture Fickian diffusivity with cross-terms is developed from irreversible thermodynamics and shows that mixture Fickian diffusivities can be expressed as the product of corrected diffusivities and a thermodynamic factor that accounts for concentration dependence. The number of unknown variables for Fickian diffusivities is the same as the number for Onsager coefficients or Maxwell−Stefan diffusivities. Adso...

Mixture Diffusion in Nanoporous Adsorbents: Development of Fickian Flux Relationship and Concentration-Swing Frequency Response Method

A mathematical model is developed for examining the influence of nonisothermal effects and accumulation of heavy alkanes on natural gas storage cycles. The model is solved for the charge and discharge steps of the cycle. This is the first study to solve the natural gas storage problem for a nonisothermal charge of natural gas containing impurities. We examine both adiabatic and isothermal operation of natural gas and pure methane storage cycles on BPL carbon and an activated carbon prepared from coconut shells. Our simulations show for both carbons that the adiabatic gas storage cycles operate under subcooled conditions with respect to the feed temperature due to long discharge times and the desorption heat. It is also shown that degradation of gas storage performance due to impurities depends more on selectivity of the material for heavy alkanes than on adsorption capacities.

Natural gas storage cycles: Influence of nonisothermal effects and heavy alkanes

A novel method is used to describe adsorption equilibria of nonideal mixtures. The two-dimensional virial equation of state is reorganized so that contributions of single components are separated from those of mixed components. Existing single component adsorption isotherm equations, which describe pure component data better and with fewer parameters than a truncated virial series, are substituted for the pure component terms. The remaining equation of state then contains terms corresponding to the pure component isotherms and terms with virial cross-coefficients for the mixture. The method is applied first to a mixture of Langmuirian adsorbates to demonstrate a sound thermodynamic and mathematical basis. We then consider nonideal binary and ternary mixtures of carbon dioxide, hydrogen sulfide, and propane on H-mordenite and a highly nonideal mixture of n-hexane and water on activated carbon.

M. Douglas LeVan

Papers

Mixture Diffusion in Nanoporous Adsorbents: Development of Fickian Flux Relationship and Concentration-Swing Frequency Response Method

Natural gas storage cycles: Influence of nonisothermal effects and heavy alkanes

Nonideal Adsorption Equilibria Described by Pure Component Isotherms and Virial Mixture Coefficients

Periodic states of adsorption cycles. IV. Direct optimization

Mass transfer rates of oxygen, nitrogen, and argon in carbon molecular sieves determined by pressure-swing frequency response