Mercury porosimetry pore size distribution

The obtained transport parameters for the Mean-Transport-Pore-Model (it/, it/) were compared with transport parameters obtained from multicomponent counter-current diffusion in Graham s diffusion cell and from mercury porosimetry pore-size distributions. 

Pore size distribution—comparison of results by mercury porosimetry and by adsorption of nitrogen... 

Whereas at the lower end of its range mercury porosimetry overlaps with the gas adsorption method, at its upper end it overlaps with photomicrography. An instructive example is provided by the work of Dullien and his associates on samples of sandstone. By stereological measurements they were able to arrive at a curve of pore size distribution, which was extremely broad and extended to very coarse macropores the size distribution from mercury porosimetry on the other hand was quite narrow and showed a sharp peak at a much lower figure, 10nm (Fig. 3.31). The apparent contradiction is readily explained in terms of wide cavities which are revealed by photomicrography, and are entered through narrower constrictions which are shown up by mercury porosimetry. 

Porosity and pore-size distribution usually are measured by mercury porosimetry, which also can provide a good estimate of the surface area (17). In this technique, the sample is placed under vacuum and mercury is forced into the pore stmcture by the appHcation of external pressure. By recording the extent of mercury intmsion as a function of the pressure appHed, it is possible to calculate the total pore volume and obtain the population of the various pore sizes in the range 2 nm to 10 nm. 

With these facts in mind, it seems reasonable to calculate the pore volume from the calibration curve that is accessible for a certain molar mass interval of the calibration polymer. A diagram of these differences in elution volume for constant M or AM intervals looks like a pore size distribution, but it is not [see the excellent review of Hagel et al. (5)]. Absolute measurements of pore volume (e.g., by mercury porosimetry) show that there is a difference on principle. Contrary to the absolute pore size distribution, the distribution calcu-... 

In addition, mercury intrusion porosimetry results are shown together with the pore size distribution in Figure 3.7.3(B). The overlay of the two sets of data provides a direct comparison of the two aspects of the pore geometry that are vital to fluid flow in porous media. In short, conventional mercury porosimetry measures the distribution of pore throat sizes. On the other hand, DDIF measures both the pore body and pore throat. The overlay of the two data sets immediately identify which part of the pore space is the pore body and which is the throat, thus obtaining a model of the pore space. In the case of Berea sandstone, it is clear from Figure 3.7.3(B) that the pore space consists of a large cavity of about 85 pm and they are connected via 15-pm channels or throats. 

B) Pore size distribution (solid line) obtained from DDIF, in comparison with mercury (Hg) porosimetry (dashed line). The peak in the... 

As described before, the pore size of porous material ranges widely from atomic size to millimeter order. Different pore sizes are required for different applications of porous materials. Most porous materials do not have uniform pores. Pore size distribution is also an important property. Narrow pore size distribution, i.e., uniform pore size, is required for instance for filters and bioreactor beds. Mercury porosimetry and gas adsorption methods are commonly used to measure pores size and pores distribution. 

Although a number of methods are available to characterize the interstitial voids of a solid, the most useful of these is mercury intrusion porosimetry [52], This method is widely used to determine the pore-size distribution of a porous material, and the void size of tablets and compacts. The method is based on the capillary rise phenomenon, in which excess pressure is required to force a nonwetting liquid into a narrow volume. 

One of the most popular methods to measure the pore size distribution in diffusion layers is mercury intrusion porosimetry (MIP) this technique is... 

Figure 3.6. Pore size distribution by mercury porosimetry of a two-layered zirconia membrane composite.

This short overview illustrates the large complexity of the SEC processes and explains the absence of a quantitative theory, which would a priori express dependence between pore size distribution of the column packing—determined for example by mercury porosimetry—and distribution constant K in Equation 16.4. Therefore SEC is not an absolute method. The SEC columns must be either calibrated or the molar mass of polymer species in the column effluent continuously monitored (Section 16.9.1). 

For the detailed study of reaction-transport interactions in the porous catalytic layer, the spatially 3D model computer-reconstructed washcoat section can be employed (Koci et al., 2006, 2007a). The structure of porous catalyst support is controlled in the course of washcoat preparation on two levels (i) the level of macropores, influenced by mixing of wet supporting material particles with different sizes followed by specific thermal treatment and (ii) the level of meso-/ micropores, determined by the internal nanostructure of the used materials (e.g. alumina, zeolites) and sizes of noble metal crystallites. Information about the porous structure (pore size distribution, typical sizes of particles, etc.) on the micro- and nanoscale levels can be obtained from scanning electron microscopy (SEM), transmission electron microscopy ( ), or other high-resolution imaging techniques in combination with mercury porosimetry and BET adsorption isotherm data. This information can be used in computer reconstruction of porous catalytic medium. In the reconstructed catalyst, transport (diffusion, permeation, heat conduction) and combined reaction-transport processes can be simulated on detailed level (Kosek et al., 2005). 

The new composite (SC-155) and some of its precursors and derivatives were characterized by LOI (loss on ignition), XRD ( X ray diffraction), 1R (infrared spectra), BET specific surface area, nitrogen adsorption desorption isotherms, pore size distribution (mercury porosimetry), dynamic methylene blue adsorption and SEM (Scanning Electron... 

Pore size distributions are often determined by the technique of mercury intrusion porosimetry. The volume of mercury (contact angle c. 140° with most solids) which can be forced into the pores of the solid is measured as a function of pressure. The pore size distribution is calculated in accordance with the equation for the pressure difference across a curved liquid interface,... 

Another method of estimating the pore size distribution of meso- and macropores is by mercury porosimetry. Here one measures the volume of mercury, a nonwetting liquid, which is forced under pressure into the pores ofa catalyst sample immersed in mercury. The pressure required to intrude mercury into the sample s pores is inversely proportional to the pore size [86]. For cylindrical pores of radius r, this... 

Mercury porosimetry measurements for a partially sintered alumina preform showed a bimodal pore size distribution with neck diameter Dn = 0.15 pm [Manurung, 2001], As a comparison with the pore sizes and distribution of the preform measured by porosimetry, SEM micrographs (Fig. 5.1) were taken before and after infiltration. Based on SEM examination, the pores in the preform before infiltration ranged in size from r 0.1-0.5 pm. Assuming an average pore radius of 0.3 pm, this radius is approximately four times larger than the pore-neck radius (Dn = 0.15 pm, so pore radius = 0.075 pm) determined by mercury porosimetry. 

In prepared catalysts the pore sizes may be quite uniform. However, in most naturally occurring materials there is a wide range of pore sizes. The actual pore size distribution can be obtained from methods such as porosimetry, in which a nonwetting liquid (usually mercury) is pumped into a solid sample [12,13,15,26,30,55]. The solid is considered to be composed of a bundle of capillaries. For each capillary, the Laplace equation (see Section 3.2.2) gives the pressure drop across a curved liquid surface ... 

Mercury porosimetry is the most suitable method for the characterization of the pore size distribution of porous materials in the macropore range that can as well be applied in the mesopore range [147-155], To obtain the theoretical foundation of mercury porosimetry, Washburn [147] applied the Young-Laplace equation... 

The poly-[HIPE] sample intrusion mercury porosimetry study reported in Figure 4.67 was carried out in a Micromeritics, Atlanta, GA, USA, AutoPore IV-9500 automatic mercury porosimeter.1 The sample holder chamber was evacuated up to 5 x 10-5 Torr the contact angle and surface tension of mercury applied by the AutoPore software in the Washburn equation to obtain the pore size distribution was 130° and 485mN/m, respectively. Besides, the equilibration time was 10 s, and the mercury intrusion pressure range was from 0.0037 to 414 MPa, that is, the pores size range was from 335.7 to 0.003 pm. The poly-(HIPE) sample was prepared by polymerizing styrene (90%) and divinylbenzene (10%) [157],... 

The porosity of AKP-30 (AKP-15) tubes, made with optimum [APMA] was 42.5% (43.2%) after firing at 500°C, measured with the Archimedes method by immersion in mercury. The sintered compacts had a porosity of 34.8% (34.5%). Their pore-size distributions, measured by mercury porosimetry are given in Figure 3. The mean pore radius was found to be 60 (92) nm. 

Scaffold porosity and information on the pore size distribution can be obtained from intrusion techniques. The most commonly used methods are mercury porosimetry and capillary flow porometry. In mercury porosimetry the pressure required to fill a tissue scaffold with non-wetting mercury is monitored over a set period of time. Higher pressures are required to fill small pores than large pores a fact that can be exploited using the Washburn equation13 to extract structural information where D is the diameter of the pore at a particular differential... 

Table 4. Porosities and pore size distributions derived from mercury intrusion porosimetry.

Figure 5 compares the pore size distributions of the scaffold computed from the intrusive techniques of capillary flow porosimetry and mercury porometry. From this figure it is apparent that the range of pore sizes derived from capillary flow porometry occurs over a smaller length scale than those based on mercury porometry data. This difference is expected since underlying physics of the... 

The distribution of pore sizes can be obtained from both mercury porosimetry and capillary flow porometry. These distributions are only representations of the actual scaffold structure reflecting the limitations of the underlying physics behind each technique. For this reason it is very difficult to compare pore size distributions for complex structures, such as particulate-leached tissue scaffolds. 

We found the latter factor-voids to be important. Experimental results showed that when green coke was calcined under the new methods, and the derived calcined coke was observed by scanning electron microscopy (Figure 2) and its pore size distribution was measured by mercury porosimetry (Figure 3), microcracks of significant sizes (1 to 60 microns) were developed. This was an important contribution to the reduction of the thermal expansion coefficients of the calcined coke processed under the new method. 

Figure 3. Apparent Pore Size Distribution of Desulco by Mercury Porosimetry.

Surface areas and pore size distributions of mesoporous materials are most easily studied by nitrogen adsorption and nitrogen capillary condensation. The most appropriate method for the study of macroporosity is mercury porosimetry [6,7], a technique which will not be treated here. 

Experimental techniques commonly used to measure pore size distribution, such as mercury porosimetry or BET analysis (Gregg and Sing, 1982), yield pore size distribution data that are not uniquely related to the pore space morphology. They are generated by interpreting mercury intrusion-extrusion or sorption hysteresis curves on the basis of an equivalent cylindrical pore assumption. To make direct comparison with digitally reconstructed porous media possible, morphology characterization methods based on simulated mercury porosimetry or simulated capillary condensation (Stepanek et al., 1999) should be used. 

---