Study of molecular sieve carbons. Part 2.—Estimation of cross-sectional diameters of non-spherical molecules

Koresh, Jacob E.; Soffer, Abraham

doi:10.1039/f19807602472

Cited by 83 publications

(43 citation statements)

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“…This is exactly the same behaviour as that observed for hard materials 51 . We thus think that the size sequence of the three gases established from CMS adsorption experiments is also valid for dipeptide crystals.…”

Section: Adsorption Isotherms and Monocomponent Selectivitiessupporting

confidence: 88%

“…The Lennard-Jones atomic diameter of Ar and minimum molecular widths of N2 and O2 have been estimated as 0.32, 0.34 and 0.31 nm, respectively 51 , all clearly below the pore sizes of the dipeptide crystals used.…”

Section: Adsorption Isotherms and Monocomponent Selectivitiesmentioning

confidence: 85%

“…The Lennard-Jones minimum width serves as a good indicator of cut-off size for sieving but is not the best measure of the most energetically favourable intermolecular distance. From the Lennard-Jones potential, this distance can be estimated as 2 1/6 times the minimum width, that is, 0.36, 0.38 and 0.34 nm, respectively 51 . It has long been known that molecules even slightly bigger than the pore/constriction experience a significantly lower adsorption potential 51 , which is precisely why CMSs are able to have very high kinetic selectivities.…”

Section: Adsorption Isotherms and Monocomponent Selectivitiesmentioning

confidence: 99%

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Hydrophobic dipeptide crystals: a promising Ag-free class of ultramicroporous materials showing argon/oxygen adsorption selectivity

Afonso

Mendes

Gales

2014

Phys. Chem. Chem. Phys.

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The adsorption isotherms of nitrogen, oxygen and argon in four VA-class hydrophobic dipeptides are presented. Isotherms were determined at 5, 20 and 35 ºC, for a pressure range of 0-6 bar. Under these conditions, adsorption is still in the Henry region. For all materials and temperatures, the sequence of preferential adsorption is Ar>O2>N2, a highly abnormal result. At 5 ºC, the dipeptide with the smallest pores, VI, has Ar/O2 adsorption equilibrium selectivities up to 1.30, the highest ever measured in Ag -free adsorbents. Gas uptakes, at 1 bar and 20 ºC, are ~0.05 mol·kg -1 , very low relative values that are partially explained by the low porosity of the solids (< 10 %). The significance of these results for the development of new materials for the process of O2 generation by pressure swing adsorption (PSA) is discussed. The results indicate some of the structural and chemical properties that prospective Ag-free adsorbents should have in order to have Ar/O2 selectivity; hydrophobic pores, less than 0.5 nm-wide, and porosity of, at least, 20 %.

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Section: Adsorption Isotherms and Monocomponent Selectivitiessupporting

confidence: 88%

Section: Adsorption Isotherms and Monocomponent Selectivitiesmentioning

confidence: 85%

Section: Adsorption Isotherms and Monocomponent Selectivitiesmentioning

confidence: 99%

See 1 more Smart Citation

Hydrophobic dipeptide crystals: a promising Ag-free class of ultramicroporous materials showing argon/oxygen adsorption selectivity

Afonso

Mendes

Gales

2014

Phys. Chem. Chem. Phys.

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“…However these methods are not suitable for liquid phase investigations. Koresh and Soffer [13] worked on the estimation of critical molecular dimensions of non-spherical molecules. They calculated the molecule volume from the molar volume.…”

Section: Calculation Of Critical Molecular Dimensionsmentioning

confidence: 99%

Adsorptive Water Removal from Organic Solvents in the ppm‐Region

Pahl

Pasel

Luckas

et al. 2010

Chemie Ingenieur Technik

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Highly pure organic solvents gain more and more importance in optical, electronical, pharmaceutical and chemical industry. In this context the removal of water in the lower ppm-and ppb-range is a major challenge since water is always present, e. g., air humidity, and leads to catalyst poisoning and undesired side reactions. One technique to remove water is by adsorption on zeolites, silica gels or aluminas. Despite single technical solutions already existing, systematic measurements of influencing parameters are still missing. The research project adresses the adsorption of water from different organic solvents. In the following experiments with linear primary alcohols and acetic acid esters are discussed as these solvents are often used in industry in low water content qualities. State of the ArtBurfield et al. investigated the drying of aromatic hydrocarbons, ethers, alcohols, amines and dipolar aprotic solvents such as acetone with molecular sieves, activated aluminas and silica gels. Chemicals such as calcium chloride, phosphorous pentoxide, sodium, potassium hydroxide, sodium sulphate, calcium sulphate and magnesium sulphate were also tested. They observed that high water solubilities and high dielectric constants lead to a poor drying performance, while low water solubilities in combination with low dielectric constants lead to good drying results with molecular sieves [1].Basmadjian [4] published a literature review on adsorptive drying of gases and liquids. He postulates that the isotherm for water removal from organic solvents on molecular sieves is independent from the solvent, as long as the solvent molecules cannot be adsorbed in the pores, i.e., there should be only one isotherm for a certain type of molecular sieve. As none of the isotherms he reviewed coincided perfectly with the water vapour isotherm, Basmadjian attributed the differences to reasons like regeneration of zeolites, non-equilibrium in measurements, coadsorption of solvent molecules in macropores and errors in water concentration measurement.Several authors investigated the adsorptive water removal from alcohols with molecular sieves. Teo and Ruthven [5] studied the system water/ethanol/zeolite 3A, Jain and Gupta [6] examined water/isopropanol/zeolite 4A, Paderewski and Gabrus [7] described water/n-butanol/zeolite 4A. All authors found nearly rectangular shaped isotherms typical for adsorption on zeolites. ExperimentalFor screening experiments as well as the measurement of adsorption isotherms the shaking table method was applied. Between 0.1 and 0.5 g of adsorbent were filled into an Erlenmeyer flask with 50 mL of solvent. The flasks were tightly sealed and shaken in an incubator at 20°C and 150 rpm until equilibrium was reached. A blind sample, consisting of a flask only filled with solvent, was used to detect potential water contamination from the surrounding atmosphere. Before adsorption experiments all adsorbents were prepared thermally according to manufacturer's guidelines. Sample flasks were dried in an oven prior to use. The...

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“…Koresh and Soffer (25,26) found that the pore openings of porous carbons can be affected significantly by degassing temperatures between 100 and 700°C. Because the pore structure of alumina pillared montmorillonite becomes unstable above 500°C (24), degassing was carried out at temperatures from 100 to 500°C and in a vacuum below 10 Ϫ4 Torr overnight (about 16 h).…”

Section: Influence Of Degassing Temperaturementioning

confidence: 99%

Development of Composite Adsorbents of Carbon and Intercalated Clay for N2and O2Adsorption: A Preliminary Study

Zhu

Vansant

1999

Journal of Colloid and Interface Science

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Study of molecular sieve carbons. Part 2.—Estimation of cross-sectional diameters of non-spherical molecules

Cited by 83 publications

References 0 publications

Hydrophobic dipeptide crystals: a promising Ag-free class of ultramicroporous materials showing argon/oxygen adsorption selectivity

Hydrophobic dipeptide crystals: a promising Ag-free class of ultramicroporous materials showing argon/oxygen adsorption selectivity

Adsorptive Water Removal from Organic Solvents in the ppm‐Region

Development of Composite Adsorbents of Carbon and Intercalated Clay for N2and O2Adsorption: A Preliminary Study

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