Specific Surface Area Determination for Microporous/Mesoporous Materials: The Case of Mesoporous FAU-Y Zeolites

Abstract

Rouquerol criterion and the BET equation is in accord with the geometrical surface determined by the chord length distribution method. Therefore BET surface area (S BET) is well representative of micropore surface areas of microporous materials and of total surface area of microporous/mesoporous materials. Mechanical mixtures of mesoporous MCM-41 and microporous FAU-Y powders of known surface areas were used to calculate the respective surface areas by weighted linear combination and the results were compared to the values obtained by the t-plot method. The first slope of the t-plot determined the mesopore + external surface areas (S mes+ext). The linear fit of the first slope is in general in the range 0.01 < p/p 0 < 0.17 and contains the volumes and relative pressures at which all micropores are filled (p/p 0 > 0.10). Overestimation of S mes+ext values was evident and appropriate corrections were provided. External surface areas (S ext) were obtained from the second slope of the t-plot, without noting an overestimation of S ext , thus allowing the determination of mesopore surface areas (S mes) by difference. Micropore surface areas were calculated by subtracting S mes+ext from the total surface area, S BET. As an example, this methodology was applied to the characterization a family of hierarchical microporous/mesoporous FAU-Y (FAUmes) synthesized from H-FAU-Y (H-Y, Si/Al = 15) using C18TAB as surfactant and different NaOH/Si ratio (0.05 < NaOH/Si < 0.25). By increasing the NaOH/Si ratio in synthesis of FAUmes, it was shown that as the micropore surface area decreases, the mesopore surface area increases, while the micropore + mesopore surface area remains constant. This methodology allows accurate characterization of the surface areas of microporous/mesoporous materials.

Guided Crystallization of Zeolite Beads Composed of ZSM-12 Nanosponges

“…The textural properties of all materials determined from the nitrogen adsorption-desorption isotherms are presented in Table 1. The microporous volumes have been determined by the t-plot method with the correction proposed by Galarneau et al for hierarchical zeolites [53,54]. The microporous volume of the sample 4-S, where the morphology of the starting beads is not conserved, is 0.19 cm 3 /g.…”

“…* value corresponding to the total pore volume determined on the plateau after hysteresis at p/p° = 0.91 without interparticle porosity. c Determined with corrected t-plot method[53,54]. d Vmeso = Vtot -Vmicro.…”

Analysis of the Chemical State in Y-zeolite Pores by Positron Annihilation Lifetime Spectroscopy

“…17,18,27,28,[19][20][21][22][23][24][25][26] In general, the catalytic activity was found to increase and the action as a polar adsorbent (hydrophilicity) became stronger with the number of Brønsted acid 4 sites. The specific surface area, [29][30][31] pore size distributions, 30,32,33 crystallinity, [30][31][32][33][34] and Al distribution within and outside the framework 31,[35][36][37][38] in numerous zeolites, including the Y zeolites subject of the present study, have been extensively studied both through empirical measurements and modelling. As a result, the influence of these properties on the acid strength is well characterized.…”

Investigation of the Porosity of Poly(sodium methacrylate) Hydrogels by 1H‐NMR T2‐Relaxation and Inverse Size‐Exclusion Chromatography

“…The porosity of rigid materials, such as silica particles, [ 25 ] zeolites, [ 26,27 ] or metal–organic frameworks, is commonly determined via Brunauer–Emmett–Teller analysis, [ 28,29 ] where the amount of nitrogen adsorbed within the pores is taken into consideration. [ 30 ] Mercury intrusion porosity is another adsorption‐based technique for the estimation of the porosity of materials.…”