Pore size distribution of microporous

In this paper we have presented a new model for determining the pore size distribution of microporous and mesoporous materials. The model has been tested using the adsorption isotherms on pure as well as mixtures of MCM-41 materials. The experimental data of adsorption of nitrogen at 77.4 has been inverted using regularization technique. The results of PSD by the present model are compared with the pore size obtained from other classical methods, NLDFT [16] as well as the that obtained by X-ray diffraction methods. 

Mey-Marom, A., and Katz, M. J., Measurement of active pore size distribution of microporous membranes—a new approach, J. Memb. ScL, 27, 119 (1986). 

For the actual catal5dic reaction, the distribution of meso- and micropores is of greater importance. The specific pore volume, pore size, and pore size distribution of microporous materials are determined by gas adsorption measurements at relatively low pressures (low values of p/po = pressure/saturation pressure). The method is based on the pressure dependence of capillary condensation on the diameter of the pores in which this condensation takes place. To calculate the pore size distribution, the desorption isotherm is also determined. Thus a distinction can be made between true adsorption and capillary condensation. The latter is described by the Kelvin equation (Eq. 5-95). 

A large specific surface area is preferable for providing large adsorption capacity, but the creation of a large internal surface area in a limited volume inevitably gives rise to large numbers of small sized pores between adsorption surfaces. The size of micropore determines the accessibility of adsorbate molecules to the adsorption surface so the pore size distribution of micropore is another important property for characterizing adsorptivity of adsorbents. 

However, the model is sufficiently advanced to allow it to be used constructively to compare and contrast other models. A passing note is that the final stages of modeling pore-size distributions of microporous carbons are some distance away from being realized. 

Models for the Pore Size Distribution of Microporous Materials from a Single Adsorption Isotherm... 

Pore-Size Distribution of Microporous Materiais TABLE 5 continued)... 

Figure 1 compares the pore size distribution of micropores of various substrates using the methanol adsorption technique. The activated charcoal shows a large surface area at > 100 m /g. However, many of the pores consist of micropores with radii < 1 nm. The ion-exchange resin (lER) similarly contains micropores. On the other hand, the microfibrilated fibers exhibit a surface area of 200m /g, which is as large as 10-20% of... 

Hernandez, A., Calvo, J. I., Pradanos, P., and Palacio, L. (1999). A multidisciplinary approach towards pore size distributions of microporous and mesoporous membranes. In T. S. Sprensen (Ed.),... 

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