BJH pore-size

Table 2. Characteristics of the silica templates and the corresponding carbon materials a unit cell parameter Sbet- specific surface area Vp total pore volume (at P/Po=0.95) Pore size determined according to the BJH method - Maximum value of the BJH pore size distribution peak calculated from the adsorption branch of the N2 isotherm.

Pore diameter (dp) for channel-like PMSs according to the BJH pore size distribution, which, however, underestimates the effective pore diameter by circa 1.0 nm, as shown by theoretical and geometrical calculations [48, 49] pore diameter of cage-like PMSs according to Ravikovitch and Neimark [50],... 

Fig. 4 Nitrogen adsorption-desorption isotherms at 77 K of heat-treated NH4 -exchanged MSU-Ge-2 (solid circles, adsorption data open circles, desorption data). The hysteresis observed at P/Po > 0.8 is due to the voids between the agglomerated particles. (Inset) BJH pore size distribution calculated from the adsorption branch of the isotherm...

Fig. 11 Nitrogen adsorption-desorption isotherms of mesoporous (a) NU-GeSi-1, (b) NU-GeSi-2, (c) NU-GeSi-3, and (d) NU-GeSi-4 materials. Inset. BJH pore size distribution calculated from the adsorption branch...

The N2 physisorption experiments on mesoporous NU-MGe-2 show typical type-lV adsorption branches with a distinct condensation step at relative pressure (P/Po) 0.16, suggesting well-defined mesopores. These materials have porous structure with BET surface areas in the range of 127-277 m /g, pore volumes in the range of 0.15-0.26 cm /g, and BJH pore sizes in the 2.7-2.8 nm range. These surface areas are reasonable if we consider the heavier inorganic frameworks and correspond to silica equivalent surface areas of 403-858 m /g. The framework wall thickness was found to be 2 run for mesoporous NU-MGe-2 (M = Sb, In, Sn, and Cd) and 2.4 nm for NU-PbGe-2, which is consistent with the larger diameter of the incorporated Pb atoms. 

Surfactants (C TMAX)a Polymer Additivesb dioo (nm) BJH Pore size (nm) BET Surface area (m2/g)... 

To improve the meso-structural order and stability of the mesoporous silica ropes, a postsynthesis ammonia hydrothermal treatment (at 100 °C) was invoked. As indicated by the XRD profile in Fig. 3A, 4-5, sharp features are readily observed in ammonia hydrothermal treated samples. Moreover, after the post-synthesis ammonia treatment, the sample also possesses a sharp capillary condensation at p/po 0.35(Fig. 3B) corresponding to a much narrower BJH pore size distribution of ca. 0.12 nm (at FWHM). In other words, the mesostructures are not only more uniform but also more stable when subjected to the post-synthesis treatment. The morphology of the silica ropes remained unchanged during the ammonia hydrothermal process. The mesostructures remain intact under hydrothermal at 100 °C in water even for extended reaction time (> 12 h). 

The pore size distributions of Ti-MCM-41 synthesized in this work are shown in Fig. 2. All of the samples showed a sharp distribution without addition of TMB and the use of methanol solvent resulted in the expansion of pore channel size. The average pore sizes determined by N, adsorption were 4.0nm and 2.8nm when the added solvents were methanol and ethanol, respectively. In this case, the used surfactant was C22TMAC1. In addition, the expansion of BJH pore size of Ti-MCM-41 was observed by the addition of TMB. A broad pore size distribution was investigated by using TMB as an auxiliary chemical. The mean pore size was ca. 7.5nm in methanol solvent. 

Fig. 1. XRD pattern of Ti-MCM-41 obtained Fig. 2. Changes in BJH pore size under the various synthesis conditions. distribution of Ti-MCM-41.

Fig. 2 Nj adorption-desorption isotherm of SBAla (a) and SBAlb (b). The inset shows the BJH pore size distribution plot for SBAla.

Important trends of double-mesopore structural development resulting from the water-treatment are revealed in Figure 2 by the N2 adsorption-desorption isotherms and the corresponding BJH pore size distribution based on the desorption branch for the representative samples mentioned above. The isotherm of the normally synthesized DMS simple shows a typical irreversible type IV adsorption isotherm with two separate, well-expressed HI hysteresis loops as defined by lUPAC at relative pressures p/po of 0.2-0.45 and that of 0.8-1.0, respectively. The first condensation step on the isotherm at p/pQ=0.2-0.45 is similar to that for usual MCM-41 materials, however, obviously, this inflection at higher relative pressures differs completely from that of previously-synthesized mesoporous materials in the aspect of their effects on the mesoporous frameworks of the product, namely, this material is of a clear double mesopore size distribution. After 1 day of postsynthesis hydrothermal treatment, the properties of the samples changed dramatically. Compared with the normally synthesized DMS sample, the water-treated sample at 373K shows more steep adsorption steps at 0.25-0.4p/po and 0.8-1.0p/po, respectively, suggesting that double-... 

Figure 9. BJH pore size distribution profiles of the sample CPN-2 calcined at different tempera-tures.The samples are the same as the Figures.

The BJH pore size distributions (Fig. 3) show that at low content of A1 (Si/Al=150) the average diameter of the channels is shifted to value larger than pure siliceous MCM-41, whereas a bimodal distribution is present in the sample with higher A1 content. 

The pore structure parameters were included in Table 2. It was found that the BET s surface area and the pore volume were 803 mVg and 0.83 cm /g, respectively. Also, the BJH pore size distribution shows MCM-41 material with a quite narrow pore diameter distribution centered around 25.8A. Thus, the framework walls are 22.5A thick. 

Figure 1 presents the nitrogen adsorption and desorption isotherms with BJH pore size distribution curves for MCM-48. The isotherms are type IV according to the lUPAC... 

Pore size determined according to the BJH method - Maximum value of the BJH pore size distribution peak calculatedfrom the adsorption branch of the N2 isotherm. 

Fig. 18. PSDsfor model porous silica glasses [25]. A, B, C, and D are sample glasses prepared by quench MD the samples differ in mean pore size and porosity. The solid curves are exact geometric PSD results for the model adsorbents the dashed lines are the PSDs predicted from BJH pore size analysis of simulated nitrogen isotherms for the model porous glasses.

This value decreases only slightly from 0.38 to 0.34 with increasing metal content. The adsorption capacity decreases also with metal content. The BJH pore size distribution... 

Material dioo lattice spacing (A) dim lattice spacing (A) BET surface area (m g ) Pore volume (mL g ) BJH pore size (A)... 

Fig.3 N2 adsorption-desorption isotherms and BJH pore size distribution for SG (24h) and nanoZSM-5.

Fig. 3. Nitrogen isotherms (left) and BJH pore size distribution (right) obtained ftom the adsorption branch of samples A, B, C and D.

Fig. 3. Niteogen adsorption isotherms (A) and the corresponding BJH pore size distribution curves (B) of the mesoporous titania as-prepared (MTi02 80), modified by ceria mesoporous titania support as-prepared (CeMTi 80) and calcined at 400 °C (CeMTi 400), and gold-based catalysts calcined at 400 °C with different gold content (2 Au/CeMTi 400 and 5 Au/CeMTi 400).

Figure 11.4 Nitrogen adsorption-desorption isotherm for a silica film (designated as ZSU-38) prepared from mixtures of cationic and silicone surfactants. The materials were calcined at 500°C in air for 5 h. The corresponding BJH pore-size distribution...

Figure 8.9 SEM images and Barrett-Joyner-Halenda (BJH) pore size distribution plots for nontreated (a,c,e) and desilicated (b,d,f) ZSM-5. (Reprinted from [151], Copyright (2011) [151], with permission from Elsevier.)...

FIG. 4 BJH pore size distributions calculated using desorption isotherms for the unmodified mesoporous silica gel LiChrospher Si-100 and samples physically coated (CBPB-T24) and chemically bonded (CBPB-B22) with CBPB. (Data from Ref. 77.)... 

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