Improvement of the Kruk−Jaroniec−Sayari Method for Pore Size Analysis of Ordered Silicas with Cylindrical Mesopores

Abstract

In this work, the X-ray diffraction structure modeling was employed for analysis of hexagonally ordered large-pore silicas, SBA-15, to determine their pore width independently of adsorption measurements. Nitrogen adsorption isotherms were used to evaluate the relative pressure of capillary condensation in cylindrical mesopores of these materials. This approach allowed us to extend the original Kruk-Jaroniec-Sayari (KJS) relation (Langmuir 1997, 13, 6267) between the pore width and capillary condensation pressure up to 10 nm instead of previously established range from 2 to 6.5 nm for a series of MCM-41 and to improve the KJS pore size analysis of large pore silicas.

Physical Adsorption Characterization of Nanoporous Materials

“…An improvement for pore size analysis can be obtained by calibrating the Kelvin equation using a series of MCM-silicas of known pore diameter (obtained from XRD interplanar spacing and the mesopore volume). In this manner, a relation between capillary condensation pressures and pore size can be established and used to obtain an empirically corrected Kelvin equation valid over the calibrated range (∼ 2 -10 nm) [118,119].…”

SBA-15 silicas containing sucrose

“…As it can be seen from the KJS analysis, more than 80% of the total pore volume is connected with the presence of mesopores bigger than 5 nm, and less than 20% is due to the presence of interconnecting pores (micropores and mesopores smaller than 5 nm). As can be seen from the Table 1, the volume of the mesopores [20], g Volume of the pores bigger than 5 nm by KJS method [20] (V 2_KJS ) decreases significantly with an increasing amount of sucrose; the volume of pores less than 5 nm (V 1_KJS ) also decreases (apart from the N2-100 sample). The V 1 /V 2 ratio for the all series (apart N20-X one) is around 0.11-0.14.…”

“…2, and small S BET values). Pore sizes were calculated using BJH [19] (for all the samples) and KJS [20] (for the series NX-100) method (d BJH and d KJS , respectively), which are commonly used to calculate pore size distributions of SBA-15 materials. However, the BJH method tends to underestimate the average pore size, so usually the KJS method is recommended for more accurate calculations.…”

Pore size distribution of micelle-templated silicas studied by thermoporosimetry using water and n-heptane

“…Average pore diameters have been evaluated from the nitrogen desorption branch according to the Broekhoff and De Boer (BdB) method. The mesopore size distributions were calculated from the desorption branch using the classical BJH scheme [26] as well as an improved Kruk-Jaroniec-Sayari model (KJSi, [27]). The latter approach, utilizing instead the Kelvin equation an empirical function with fitted parameters for quantification of the pore size vs. partial pressure relation, gives for the micelle-templated silicas the pores size distributions that are in very good agreement with those computed using NL-DFT method.…”