Pore diameter distribution

The commercial mercury porosimeters can usually provide pore diameter distribution data in the range of 3.5 nm to 7.5 microns. It is a useful and commonly used method for characterizing porous particles or bodies. Figure... 

A number of analytical instruments helped us to probe and understand our catalysts in greater detail. Although these may be standard equipment for a large manufacturer or large petroleum research laboratory, we had to acquire them and train our personnel in their use before we could proceed. Some of the more vital instruments included equipment for measuring surface area, pore volume and pore diameter distribution, and X-ray... 

DZ-40 has the properties of pore volume and pore diameter distribution listed in Table 111.(11) Note the considerable pore volume in the 100-1000 Angstroms range (Figure 11). Figure 12 also shows some of our data indicating the benefit of a larger pore volume. It appeared to us that an optimum for catalysts in resid cracking occurs between 0.40 and 0.55 cc/gm. 

The sharp steps in the isotherms at a relative pressure p/po = 0.28 in case of the pristine MCM-48 silica and 0.23 for the transition metal containing silica reveal the high order of the mesoporous systems. The hysteresis starting at a relative pressure of p/po = 0.47 arises from a second porous system, which will be discussed elsewhere. Applying the BJH theory to the adsorption isotherms of all three samples the pore diameter distributions can be calculated. 

The pore diameter distribution of the pristine MCM-48 material shows a sharp maximum with a mean pore diameter of 2.49 nm (figure 4). 

Pore diameter distribution very broad narrow narrow... 

Fortunately, the effects of most mobile-phase characteristics such as the nature and concentration of organic solvent or ionic additives the temperature, the pH, or the bioactivity and the relative retentiveness of a particular polypeptide or protein can be ascertained very readily from very small-scale batch test tube pilot experiments. Similarly, the influence of some sorbent variables, such as the effect of ligand composition, particle sizes, or pore diameter distribution can be ascertained from small-scale batch experiments. However, it is clear that the isothermal binding behavior of many polypeptides or proteins in static batch systems can vary significantly from what is observed in dynamic systems as usually practiced in a packed or expanded bed in column chromatographic systems. This behavior is not only related to issues of different accessibility of the polypeptides or proteins to the stationary phase surface area and hence different loading capacities, but also involves the complex relationships between diffusion kinetics and adsorption kinetics in the overall mass transport phenomenon. Thus, the more subtle effects associated with the influence of feedstock loading concentration on the... 

Adsorption isotherms were recorded with a Micromeritics ASAP 2010 instrument. Experimental porous data (surface area, volume, pore diameter distribution) have been... 

Figure 2 By use of Eq (2), from an assumed pore diameter distribution density V(d) (full line) follows the corresponding CLD A [) (dashed line), Basic behaviour and maximum positions of K(rf) and A [) nearly agree.

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. 

If a large number of open-ended cylindrical pore segments (like the one in Fig. 2) are interconnected such that the diameter of any pore is independent of the size of neighbor pores, a so-called randomized, or stochastic, pore network is formed. Such a set can be assembled from a cohort obeying any stipulated pore diameter distribution function. If all the pore segments are of equal length with a connectivity of 4, a square network... 

In the selection of the stationary and mobile phase, a variety of chemical and physical factors of the chromatographic system that may contribute to the variation in the resolution and recovery of natural products need to be considered. The stationary phase contributions relate to the ligand composition, ligand density, surface heterogeneity, surface area, particle size, particle size distribution, particle compressibility, pore diameter, and pore diameter distribution. The mobile phase contributions relate to the type of organic solvents, eluent composition, ionic strength, pH, temperature, loading concentration, and volume. 

The breadth of the pore diameters distribution in CPGs is usually less than 10 %. 

Fig. 4. Horvath-Kawazoe pore diameter (r) distribution of MSU-1-1 (left) and BJH pore diameter distribution of MSU-1 (right).

Figure 2. Comparison of the pore diameter distribution curves of a silica gel and a precipitated silica (33). V and R denote volume and radius, respectively.

For the various carrier gas flow rates, the experimentally obtained values of the effective diffusivity are given in Table 2 and represented graphically in Figure 3. Table 2 contains also the values of the effective di-ffusivity that were theoretically deduced from the pore diameter distribution by applying either the Johnson-Stewart model (ref. 3) or the Wakao-Smith model (ref. 4). 

The variations in the effective diffusivities as a function of the porous structure of the supports coincide neither for the theoretical values nor for the experimental values. As the previous discussion has already shown, the effective diffusivity cannot be estimated from the pore diameter distribution. The arrangement of micropores and macropores must be known. While it is true that stochastic model of porous structure such as those put forward by Mann and Golshan (ref. 8) might allow the arrangement of the different pores to be represented, the resolution of these models in a chemical reaction appears too complicated. 

Fig.3. Pore diameter distribution curves of power ZSM-5 seed and ZSM-5 disc obtained by...

Nitrogen adsorption properties of typical samples, amorphous sinter, powder zeolite ZSM-35 and zeolite ZSM-35 disc, were measured on a Micromeritics ASAP 2000 at 77k. According to the pore diameter distribution curve in fig.3, zeolite ZSM-35 disc had similar micropore to powder zeolite ZSM-35. Results can be seen from Table 6, the pore diameter of zeolite ZSM-... 

The microstructure of the green body as observed by SEM is shown in Fig. 4. After consolidation, powders in green body compact closely and homogeneously. However, the polymer network was not observed via SEM. The pore diameter distribution, obtained by Hg intrusion porosimetry, showed a monomodal distribution type. The relative density, porosity, and the median pore diameter of green samples were 57.67%, 35.02%, and 10.6nm, respectively. 

As a amidified approach, only mean values of the molecular size and pore diameter distribution were used. The above results were then substituted into the... 

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