Pore size distribution PSD

The models of Matranga, Myers and Glandt [22] and Tan and Gubbins [23] for supercritical methane adsorption on carbon using a slit shaped pore have shown the importance of pore width on adsorbate density. An estimate of the pore width distribution has been recognized as a valuable tool in evaluating adsorbents. Several methods have been reported for obtaining pore size distributions, (PSDs), some of which are discussed below. 

Figure 9.26 The scheme of the simple interrelation of pore size distributions (psd), particle size distributions (PSD), and particles space arrangement (PSA).

Prior to nitrogen adsorption experiment to determine surface properties, ACC sample was degassed at 130°C under vacuum (up to 10 torr) for 12 h. The adsorption data were obtained at the Central Laboratory of Middle East Technical University (METU) with a Quantachrome Autosoib-l-C/MS apparatus over a relative pressure ranging from 10" to 1. The BET specific surface area, total pore volume, micropore volume, mesopore volume, and pore size distribution, PSD, of ACC were yielded by using the software of the apparatus. 

The pore size distribution (PSD) for mesopores and micropores were calculated using DFT (Density Funetional Theory) method and the resulting distribution curves are given in Fig. 21.3. Total mesopore volume (V ) was determined as 0.022 cm g and total mieropore volume (V. ) was determined as 0.709 em g from the eorresponding method. The ACC consists of pores mainly in micro character (<20 A) as seen both from Fig. 21.3. The pH value of ACC used in this study had been previously found to be 7.4 [4]. 

Determination of Pore Size Distributions. The shape and range of a GPC calibration curve are, in part, a reflection of the pore size distribution (PSD) of the column packing material. A consideration of the nature of PSDs for the ULTRASTYRAGEL columns to be used in this work is therefore appropriate. The classical techniques for the measurement of PSDs are mercury porisimetry and capillary condensation. The equipment required to perform these measurements is expensive to own and maintain and the experiments are tedious. In addition, it is not clear that these methods can be effectively applied to swellable gels such as the styrene-divinylbenzene copolymer used in ULTRASTYRAGEL columns. Both of the classical techniques are applied to dry solids, but a significant portion of the pore structure of the gel is collapsed in this state. For this reason, it would be desirable to find a way to determine the PSD from measurements taken on gels in the swollen state in which they are normally used, e.g. a conventional packed GPC column. 

Figures 4a and 4b depict selected Nitrogen adsorption-desoprtion isotherms and pore size distributions (PSDs) for the same series of samples. As seen here and also in Table 1, all hexagonal phases exhibited pore sizes mostly above 5 nm, while typical pore sizes of MCM-41 silica prepared in the presence of CTAB under more common temperatures, i.e., 80 - 120 °C, have 3.5 to 4 nm pores [5, 19]. Earlier work showed that direct synthesis or postsynthesis hydrothermal restructuring in the mother liquor at high temperature, e.g. 150 °C gave rise to...

In a thermoporosimetry experiment, the whole DSC curve is indeed representative of the pore size distribution of a given sample. From Equation 10.5 and the DSC thermogram, the pore size distribution (PSD) can be derived as follows ... 

The physical and chemical activation processes have been generally employed to prepare the porous carbons.18"35 However, the pore structures are not easily controlled by the activation processes and the size of the pores generated by the activation processes is limited to the micropore range only. Recently, much attention has been paid to the synthesis of meso/macroporous carbons with various pore structures and pore size distributions (PSD) by using various types of such inorganic templates as silica materials and zeolites.17,36 55... 

Figure 10. Nyquist plot of the impedance spectrum experimentally measured on the ACFCE at an applied potential of 0.1 V (vs. SCE) in a 30 wt % H2SO4 solution. Dotted and solid lines represent the impedance spectra theoretically calculated based upon the transmission line model (TLM) in consideration of pore size distribution (PSD) and pore length distribution (PLD), respectively. Reprinted with permission from G. -J. Lee, S. -I. Pyun, and C. -H. Kim, J. Solid State Electrochem., 8 (2004) 110. Copyright 2003, with kind permission of Springer Science and Business Media.

On the other hand, for the microporous carbons with pore size distribution (PSD) with pore fractality, the pore fractal dimensions56,59,62 which represent the size distribution irregularity can be theoretically calculated by non-linear fitting of experimental adsorption isotherm with Dubinin-Astakhov (D-A) equation in consideration of PSD with pore fractality.143"149 The image analysis method54,151"153 has proven to be also effective for the estimation of the surface fractal dimension of the porous materials using perimeter-area method.154"159... 

For obtaining more detailed information on the pore structure, pore size distribution (PSD) curves were determined by the application of the density functional theory (DFT) method to the N2 adsorption isotherms (Figure 3.20). The PSD curve of PFA-P7-H is very sharp and most of the... 

Porous carbon materials mostly consist of carbon and exhibit appreciable apparent surface area and micropore volume (MPV) [1-3], They are solids with a wide variety of pore size distributions (PSDs), which can be prepared in different forms, such as powders, granules, pellets, fibers, cloths,... 

In Chapters 4 and 6, several methods of characterization of solids that are normally used for catalyst testing were described. In particular, the parameters which characterize the surface morphology of a porous catalyst are the same that characterize a porous adsorbent, that is, the specific surface area, S [m2/g], the micropore volume, W1 [cm3/g], the sum of the micropore andmesopore volumes, that is, the pore volume, W [cm3/g], and the pore size distribution (PSD), AVp/ADp (see Chapter 6). 

In these adsorbents an increase in carbon deposit content leads to reduction of the total pore volume, but an enhancement of the specific surface area (Sbet) and contribution of nanopores because the FDA value increases. A noticeable increase in nanoporosity of these carbosils is accompanied by significant changes in the pore size distributions (PSDs) at Rp < 2 nm (Figure 2). 

The applied pressure is related to the desired pore size via the Washburn Equation [1] which implies a cylindrical pore shape assumption. Mercury porosimetry is widely applied for catalyst characterization in both QC and research applications for several reasons including rapid reproducible analysis, a wide pore size range ( 2 nm to >100 / m, depending on the pressure range of the instrument), and the ability to obtain specific surface area and pore size distribution information from the same measurement. Accuracy of the method suffers from several factors including contact angle and surface tension uncertainty, pore shape effects, and sample compression. However, the largest discrepancy between a mercury porosimetry-derived pore size distribution (PSD) and the actual PSD usually... 

It is the scope of the present work to investigate the potential of the CPSM model [8,9], to simulate composite gas sorption isotherms exhibiting or not hysteresis and hence the evaluation of a unified pore size distribution (PSD) covering both the micro-and meso-pore range. Additionally, micropore volume and surface areas will be calculated via the integration... 

Physico-chemical techniques are widely used for characterization of catalysts and porous materials in general. Well-known methods based on physical adsorption of inert gases (N2 and CO2) and penetration of mercury at elevated pressures provide information on the total surface area, pore volume, and pore size distribution (PSD) of the sample [1,2]. Gas adsorption and mercury porosimetry are often compared since they generate data of similar nature in the pore size range 4 - 100 nm. 

The Horvath-Kawazoe (HK) method is capable of generating model isotherms more efficiently than either molecular simulation (MS) or density functional theory (DFT) to characterize the pore size distribution (PSD) of microporous solids. A two-stage HK method is introduced that accounts for monolayer adsorption in mesopores prior to capillary condensation. PSD analysis results from the original and two-stage HK models are evaluated. 

The maximum of the pore size distribution (PSD) curve, D ax (nin) cis well as the variance of distribution 2a (nm). These parameters are important since they express the maximum and... 

Figure 2. Typical Nitrogen adsorption-desorption isotherms at 77K and the corresponding pore size distribution PSD curves (dotted line —). The points (o) and ( ) are the experimental adsorption-desorption data connected by a light line. The darker line corresponds to the CPSM simulation. The PSD derived according th the CPSM model are also given by the continuous line (—).

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