Mercury porosimetry method cylindrical pore

Lindstrom and Boersma (1971) pioneered the prediction of breakthrough curves from equivalent cylindrical pore size distributions, determined by either the water retention or mercury porosimetry methods. The model developed by these authors includes the effects of bothintra- and interpore dispersion. In general, dispersion due to differences in tube size has a much greater influence on the shape and position of the breakthrough curve than mixing within tubes due to microscopic velocity profiles (Rao et al., 1976). For completeness, however, it is preferable to include both effects. Lindstrom and Boersma (1971) defined a CDE for each tube, so that C/C0 for the bundle as a whole is given by ... 

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... 

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. 

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... 

The surface area of MCM-41 obtained by mercury porosimetry, calculated using the Rootare-Prenzlow equation, " is lower than that found by the adsorption method, as shown in Table 2. In general for MCM-41, the surface areas obtained were in the following order mercury porosimetry < gas adsorption < SAXS < SANS. The mesopore diameters of the MCM-41 studied in the current work are in the range of 2.3 - 4.4 nm, and the lowest diameter of the cylindrical pores in which mercury can penetrate (at the highest pressure studied in this work) is about 3.2 nm. Therefore, if the walls of the pores are rigid, for the samples C14-C18 the surface area reported by mercury porosimetry is too low. 

Alumina membranes containing monodispersed cylindrical pores have been characterised by a combination of three ditferent techniques Field emission scanning electron microscopy, mercury porosimetry and small angle neutron scattering (SANS). SANS is a method which can provide details of the highly anisotropic texture in such model porous materials. 

The highly anisotropic porous texture of alumina membranes containing monodispersed cylindrical pores has been characterised using a combination of three techniques SEM, mercury porosimetry and SANS. The SANS technique is a promising and very sensitive method for the analysis of such anisotropic pore structures. Further quantitative analysis of these membranes, which contain uniform macropores, will require SANS measurements at much lower Q. 

In Table 1 the results obtained from the textural characterization of the supports and catalysts by nitrogen adsorption and mercury intrusion porosimetry are presented. In the table the values of surface area obtained from the gas adsorption results, using the BET method for which the linear portion was usually located in the relative pressure range of 0.05 to 0.3 Sbet [9], and those from the intrusion curve of the porosimetry analysis, using a nonintersecting cylindrical pore model Sng [10], are shown. The pore volume Vp is that recorded at the liighest intrusion pressure reached during the porosimetry analysis, and as such represents the pore volume of pores between ca. SOpm to 3mn pore radius. The pore radii were taken from the maxima of the curves of pore size distribution. 

Mercury (Hg) porosimetry is a method that is able to probe about six orders of magnitude in accessible pore size ranging from about 400 pm down to a few Angstroms [76]. Hereby isostatic pressure is applied to force nonwetting hquid mercury into the pores to be quantified. The external pressure required to access a cylindrical pore with radius Rpore is given by the Washburn equation ... 

A well-known method for characterization of porous materials is mercury porosimetry. Mercury has a high surface tension and has to be forced into the pores of the material in order to fill the pores. From the uptake of mercury as a function of pressure one can calculate the pore size distribution based on volume in terms of equivalent cylindrical capillaries. The total uptake of mercury at the maximum applied pressure gives the porosity. 

A simple model for the pore volume or the void space in a porous material is to assume it to be composed of a collection of cylindrical pores of radius r. Then a volume of a liquid that does not wet the pore wall surfaces can be forced under pressure to fill the void space. This liquid is invariably mercury because it has a high surface tension, thus the Hg penetration (or porosimetry) method is used to determine pore volumes and the pore size distribution of larger pores, i.e., those with radii larger than about 10 nm. The relationship between pore size and applied pressure. Pap, is obtained by a force balance, that is, the force due to surface tension is equated to the applied force ... 

Mercury porosimetry (MP) is an extremely useful technique to characterize pore structure of materials (Giesche, 2006). This method measures an average diameter of open pores and its distribution, total volume of pores, specific surface, density, etc. Limitation of this method is that high pressures can distort the actual pore structure. Besides it does not give the actual size of pores or capillaries, but equivalent diameter of model cylindrical pores. Closed pores are inaccessible to mercury and cannot be studied. 

Mercury intrusion porosimetry is a convenient method of determining pore size distributions within the range 15 x 10" -2 x 10 m. Let us consider a uniform cylindrical pore of radius r, which intersects the surface of a porous pellet. If the pellet is placed in a chamber that is first evacuated and... 

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