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Robens, E.; Keller, JU; Massen, CH Carel; Staudt, Reiner

doi:10.1023/a:1010195013633

“…For water isotherms, the Gravimetric Sorption Analyzer was operating in a flow mode, which provides a more accurate measurement of condensable vapors 15. The standard degassing procedure as above was undertaken to remove air and water vapor.…”

Section: Methodsmentioning

confidence: 99%

Sorption of methane, nitrogen, carbon dioxide, and water in Matrimid 5218

Scholes

¹

,

Tao

²

,

Stevens

³

et al. 2010

J of Applied Polymer Sci

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The sorption of the light gases CH 4 , N 2 , CO 2 as well as water into polymer films prepared from a commercial sample of 3,3 0 -4, 4 0 -benzophenone tetracarboxylicdianhydride diaminophenylindane (Matrimid 5218) are measured. The light gas isotherms follow standard dualsorption behavior for polymeric films with the Henry's Law coefficient correlated to the Lennard-Jones well depth parameter. Water sorption behavior was similar to rubbery polymers, that of significant adsorption into the polymeric matrix and was modeled by Henry's law exclusively.

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“…Ross and Olivier, Webb and Orr, and more recently Robens et al . addressed in detail the issues of apparatus calibration, thermal transpiration, and the ideal and nonideal behavior of gaseous helium and nitrogen, respectively, at cryogenic temperatures. Calculation of the departure from ideal gas behavior, even at low pressure, is essential for accurate isothermal adsorption data.…”

Section: Introductionmentioning

confidence: 99%

Analysis of Uncertainties in Manometric Gas-Adsorption Measurements. I: Propagation of Uncertainties in BET Analyses

Badalyan

¹

,

Pendleton

²

2003

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A detailed analysis and calculation of the uncertainties associated with manometric gas-adsorption measurements are presented for experimental data for nitrogen adsorption at ≈77 K by a traceable standard carbon black material (004-16820-02). Equipment-and measurement-related uncertainty sources derive from the dosing and sampling volumes; temperature control of these volumes; dosing, equilibrium, and barometric-pressure measurements; liquid nitrogen level control; and sample-mass measurements. Data processing errors derive from ignoring thermal transpiration effects and nonideal gas behavior. Departure from ideal gas behavior contributions to the amount adsorbed was accounted for by considering the temperature relationship of the second virial coefficient of the virial equation of state. Variation in the liquid nitrogen level control is shown to have an enormous impact on the pressure-measurement precision and, hence, the amount adsorbed. Variation of the liquid nitrogen level by (1 mm results in a variation of the equilibrium pressure from -0.42 to +0.52% and the volume of gaseous nitrogen adsorbed from -8.53 to +5.94% when compared with the results obtained during precise level control (within (0.2 mm). In addition to these uncertainty sources, reproducibility in the sample-mass measurement is important; a decrease in the mass resolution from 5 × 10 -5 to 5 × 10 -4 g generates a relative combined standard uncertainty of the volume of nitrogen adsorbed by 10-fold varying from 2.78 to 9.86% over the relative pressure range from 0.0007 to 0.98. For a similar standard mass uncertainty applied to the BrunauerEmmet-Teller specific surface area analysis, the final area relative combined uncertainty increases from 0.63 to 6.19%. The calculated cumulative relative combined uncertainty in the volume adsorbed increases continuously with each experimental point from 0.28 (for the first experimental point on the adsorption branch of the isotherm) to 9.54% (for the last experimental point on the desorption branch of the isotherm), with subsequent implications for mesopore modeling and analysis accuracy.

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“…This irreproducibility has also been shown in interlaboratory studies in which participating laboratories have made isotherm measurements, ostensibly on the same material, yet obtained greatly varied results [9][10][11][12][13][14][15][16][17]. Factors contributing to the irreproducibility can arise anywhere along the multistep procedure leading to the adsorption isotherm data [18][19][20]. These procedures can include material synthesis (starting materials, solvents, conditions, treatment), sample preparation (activation, outgassing, storage, weighing, transfer), the gas adsorption measurements themselves (calibration, sample volume, measurements of temperature, pressure, and mass), data processing (equation of state, buoyancy correction, blank correction), and data reporting (results, experimental details).…”

Section: Introductionmentioning

confidence: 84%

Reference surface excess isotherms for carbon dioxide adsorption on ammonium ZSM-5 at various temperatures

Nguyen

¹

,

Toman

²

,

Martinez

³

et al. 2022

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This work is part of the effort at the Facility for Adsorbent Characterization and Testing (FACT lab) at the National Institute of Standards and Technology (NIST) to develop reference materials, reference data, and measurement best practices for adsorption metrology. High-pressure surface excess isotherms for CO2 adsorption on NIST Reference Material 8852 (ammonium ZSM-5) at 15 °C, 25 °C, and 35 °C are reported, expanding on a FACT Lab-organized international interlaboratory study on this sorbent/sorbate pair at 20 °C. The range of temperatures of the present study is of interest for many CO2 adsorption measurements and applications. Measurements were made using five different adsorption instruments, both manometric and gravimetric. Excellent agreement in the measured isotherms among the instruments was found. An empirical reference equation of the form,$${n}_{ex,ref}({P}_{eq})=\frac{c}{\{{1+\mathrm{exp}[\left(-\mathrm{ln}\left(P\right)+a\right)/b ]\}}^{b }} ,$$ n e x , r e f ( P eq ) = c { 1 + exp [ - ln P + a / b ] } b , [nex,ref is surface excess uptake (mmol/g); Peq is equilibrium pressure (MPa); P is (Peq)/(1 MPa)]; a, b, c are constants] and the 95% uncertainty interval were determined for the isotherms at each of the temperatures. Lastly, the isosteric heat of adsorption is estimated from absolute isotherms derived from the surface excess reference data.

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Cited by 23 publications

References 7 publications

Sorption of methane, nitrogen, carbon dioxide, and water in Matrimid 5218

Sorption of methane, nitrogen, carbon dioxide, and water in Matrimid 5218

Analysis of Uncertainties in Manometric Gas-Adsorption Measurements. I: Propagation of Uncertainties in BET Analyses

Reference surface excess isotherms for carbon dioxide adsorption on ammonium ZSM-5 at various temperatures

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