Home  About us  Contact
 

Adsorption Selectivity (adsorption + selectivity)

Distribution by Scientific Domains
Chemistry80%

Selected Abstracts

Multifunctional Microporous MOFs Exhibiting Gas/Hydrocarbon Adsorption Selectivity, Separation Capability and Three-Dimensional Magnetic Ordering,

ADVANCED FUNCTIONAL MATERIALS, Issue 15 2008
Kunhao Li
Abstract Microporous materials [M3(HCOO)6],·,DMF (M,=,Mn, Co, Ni) were synthesized solvothermally and structurally characterized by single crystal and powder X-ray diffraction methods. The metal network exhibits diamondoid connectivity and the overall framework gives rise to zigzag channels along the b axis where guest dimethylformamide molecules reside. The effective pore size of these channels is ,5,6,Å. The materials feature high thermal stability and permanent porosity with relatively small pore diameters which are attributed to the extensive strong dative bonding between the metal centers and formate molecules. The title compounds exhibit interesting multi-fold gas adsorption and magnetic properties. The adsorption study of a series of alcohols, aromatics, and linear hydrocarbons revealed strong control of the adsorbent channel structures on their adsorption capacity and selectivity. The study also indicated possibility of using these materials for separation of close boiling chemicals (e.g., ethylbenzene and p-xylene) via pressure swing adsorption (PSA) process and molecules with different diffusion parameters via kinetic-based process. Three-dimensional spontaneous magnetic ordering was found in all three network structures investigated and at ground states they behave somewhat like soft magnets. [source]

Enantioseparation with D -Phe- and L -Phe-imprinted PAN-based membranes by ultrafiltration

JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 4 2008
Noaman Ul-Haq
Abstract BACKGROUND: Solute rejection by a molecularly imprinted membrane was observed for the first time. Enantioselective poly[(acrylonitrile)-co-(acrylic acid)] membranes were prepared by a wet-phase inversion method using D -phenylalanine (D -Phe) and L -phenylalanine (L -Phe) as templates, separately, in order to compare the imprinting effects of these isomers using an ultrafiltration experiment. RESULTS: Recognition sites were successfully created in the prepared membranes, which had a nanoporous structure. The rejection selectivities of 0.13 and 0.28, adsorption selectivities of 2.25 and 2.40 and permselectivities of 1.94 and 2.08 were achieved for the D - and L -Phe-imprinted membranes, respectively, after 16 mL (34 min) of ultrafiltration. CONCLUSION: Solute rejection by a molecularly imprinted membrane was selective. The performance characteristics of both the D - and L -Phe-imprinted membranes were different. Thus, the selection of an appropriate stereoisomer as a template plays an important role in the imprinting of membranes with regard to chiral resolution by ultrafiltration. Copyright © 2008 Society of Chemical Industry [source]

Molecular modeling of H2 purification on Na-LSX zeolite and experimental validation

AICHE JOURNAL, Issue 1 2005
B. Weinberger
Analysis of hydrogen purification process by adsorption in the dehydrated Na-LSX zeolite is described. New measurements of hydrogen and nitrogen adsorption selectivity of this zeolite have been performed up to a pressure of 20 MPa and at temperatures of 273, 293 and 313 K, by using a gravimetric-volumetric method. Structural characterizations were realized by helium density displacement, nuclear magnetic resonance, X-ray diffraction and scanning electronic microscopy. Furthermore, Monte Carlo simulations of gas adsorption were performed in a zeolite model of Na-LSX, using pair potentials to represent the interaction between gas molecules and zeolite atoms. Comparison of simulation results and experimental data enabled testing of the validity of such a modeling of the gas-zeolite interaction. © 2004 American Institute of Chemical Engineers AIChE J, 51:142,148, 2005 [source]

Understanding Adsorption and Interactions of Alkane Isomer Mixtures in Isoreticular Metal,Organic Frameworks

CHEMISTRY - A EUROPEAN JOURNAL, Issue 22 2007
Li Zhang Dr.
Abstract Novel metal,organic frameworks (MOFs) may lead to advances in adsorption and catalysis owing to their superior properties compared to traditional nanoporous materials. A combination of the grand canonical Monte Carlo method and configurational-bias Monte Carlo simulation was used to evaluate the adsorption isotherms of C4,C6 alkane isomer mixtures in IRMOF-1 and IRMOF-6. The amounts of adsorbed linear and branched alkanes increase with increasing pressure, and the amount of branched alkanes is larger than that of the linear ones. The locations of the alkane isomer reveal that the Zn4O clusters of the IRMOFs are the preferential adsorption sites for the adsorbate molecules. The interaction energy between the Zn4O cluster and the adsorbate is larger than that between the organic linker and the adsorbate. It was further confirmed that the Zn4O cluster plays a much more important role in adsorption by pushing a probe molecule into the pore at positions closer to the Zn4O cluster. It is difficult for branched alkane molecules to approach the Zn4O cluster of IRMOF-6 closely owing to strong spatial hindrance. In addition, the adsorption selectivity is discussed from the viewpoints of thermodynamics and kinetics, and the diffusion behavior of n -butane and 2-methylpropane were investigated to illustrate the relationship between diffusion and adsorption. [source]

New Microporous Materials for Acetylene Storage and C2H2/CO2 Separation: Insights from Molecular Simulations

CHEMPHYSCHEM, Issue 10 2010
Michael Fischer
Abstract Force-field based grand-canonical Monte Carlo simulations are used to investigate the acetylene and carbon dioxide uptake capacity, as well as the C2H2/CO2 adsorption selectivity of three novel microporous materials: Magnesium formate, Cu3(btc)2, and cucurbit[6]uril. Because no comparable computational studies of acetylene adsorption have been reported so far, the study focuses on systems for which experimental data are available to permit a thorough validation of the simulation results. The results for magnesium formate are in excellent agreement with experiment. The simulation predicts a high selectivity for acetylene over CO2, which can be understood from a detailed analysis of the structural features that determine the affinity of Mg-formate towards C2H2. For Cu3(btc)2, preliminary calculations reveal the necessity to include the interaction of the sorbate molecules with the unsaturated metal sites, which is done by means of a parameter adjustment based on ab-initio calculations. In spite of the high C2H2 storage capacity, the C2H2/CO2 selectivity of this material is very modest. The simulation results for the porous organic crystal cucurbit[6]uril show that the adsorption characteristics that have been observed experimentally, particularly the very high isosteric heat of adsorption, cannot be understood when an ideal structure is assumed. It is postulated that structural imperfections play a key role in determining the C2H2 adsorption behavior of this material, and this proposition is supported by additional calculations. [source]