Analysis of Nitrogen Adsorption Isotherms for a Series of Porous Silicas with Uniform and Cylindrical Pores: A New Method of Calculating Pore Size Distribution of Pore Radius 1–2 nm

The Horvath–Kawazoe (H–K) method, which is frequently used to obtain the micropore size distributions of microporous materials, has been tested by Monte Carlo Simulation of nitrogen adsorption isotherms. The results show that the H–K method only gives good results when the microporosity is confined to a pore size lower than approximately 13 Å. In this region, although the method can predict the micropore size distribution peak with acceptable precision, it fails for wider distributions.

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Positronium Thermalization Process in Nanoporous Materials and its Influence on the Shape of PALS Spectrum

Materials Science Forum ◽

10.4028/www.scientific.net/msf.607.39 ◽

2008 ◽

Vol 607 ◽

pp. 39-41

Author(s):

Jerzy Kansy ◽

Radosław Zaleski

Keyword(s):

Mesoporous Silica ◽

Pore Size Distribution ◽

Porous Materials ◽

Pore Size ◽

Size Distribution ◽

Nanoporous Materials ◽

New Method ◽

New Model ◽

Conventional Models ◽

Mcm 41

A new method of analysis of PALS spectra of porous materials is proposed. The model considers both the thermalization process of positronium inside the pores and the pore size distribution. The new model is fitted to spectra of mesoporous silica MCM-41 and MSF. The resulting parameters are compared with parameters obtained from fitting the “conventional” models, i.e. a sum of exponential components with discrete or/and distributed lifetimes.

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Comparison of Nitrogen Adsorption and Mercury Penetration Results: II. Pore size Distributions Calculated from Type IV Isotherm Data

Adsorption Science & Technology ◽

10.1177/026361748800500301 ◽

1988 ◽

Vol 5 (3) ◽

pp. 168-190 ◽

Cited By ~ 6

Author(s):

Bruce D. Adkins ◽

Burtron H. Davis

Keyword(s):

Pore Size Distribution ◽

Pore Size ◽

Size Distribution ◽

Nitrogen Adsorption ◽

Type Iv ◽

Pore Size Distributions ◽

Nitrogen Desorption ◽

The Difference ◽

Penetration Data ◽

Packed Sphere

The pore distributions calculated from nitrogen desorption and from mercury penetration data are similar for the four materials utilized in this study. While there are small differences in the distributions calculated using different models (Cohan. Foster or Broekhoff-deBoer) with nitrogen adsorption or desorption isotherm data, all three show reasonable agreement with distributions calculated from mercury penetration data. Frequently practical catalysts have such a broad pore size distribution that neither method alone is adequate to measure the total pore size range. The present results suggest a direct comparison, without recourse to a scaling factor, is appropriate when comparing results from the two methods even though the pore size distribution maximum may vary by at least 50% depending upon the model chosen for the calculation. Better agreement may be obtained between the two experimental techniques by adjusting either the nitrogen adsorption data using a packed sphere model or the mercury penetration data by an earlier reported correction ratio. The difference between the two methods becomes less than 20% when a correction procedure is used; however, further studies are needed to define the range of material shaped that these procedures are applicable to.

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