Mercury penetration

In mercury penetration measurements, mercury is forced under various pressures into the pores of the material. Due to the large contact angle (0) of mercury in contact with most materials, the pressure required to force mercury into the pores can be expressed as a function of the pore radius  

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Using the curve given by the square points in Fig. XVI-2, make the qualitative reconstruction of the original data plot of volume of mercury penetrated per gram versus applied pressure. 

The technique of mercury porosimetry consists essentially in measuring the extent of mercury penetration into an evacuated solid as a function of the applied hydrostatic pressure. The full scope of the method first became apparent in 1945 when Ritter and Drake developed a technique for ... 

Fig. 332 Mercury penetration in alumina-silica gel (Kamakin" ). O, penetration A, retraction , re-penetration A. renewed retraction. (After...

Like the analogous equation for capillary condensation (Equation (3.74) Equation (3.81) is based on the tacit assumption that the pore is of constant cross-section. Integration of Equation (3.81) over the range of the mercury penetration curve gives an expression for the surface area -4(Hg) of the walls of all the pores which have been penetrated by the mercury ... 

Figure 9,16 Comparison of theory with experiment for rg/a versus K. The solid line is drawn according to the theory for flexible chains in a cylindrical pore. Experimental points show some data, with pore dimensions determined by mercury penetration (circles, a = 21 nm) and gas adsorption (squares, a= 41 nm). [From W. W. Yau and C. P. yidXont, Polym. Prepr. 12 797 (1971), used with permission.]...

Pore Volume by Nitrogen Adsorption or Mercury Penetration... 

Important physical properties of catalysts include the particle size and shape, surface area, pore volume, pore size distribution, and strength to resist cmshing and abrasion. Measurements of catalyst physical properties (43) are routine and often automated. Pores with diameters <2.0 nm are called micropores those with diameters between 2.0 and 5.0 nm are called mesopores and those with diameters >5.0 nm are called macropores. Pore volumes and pore size distributions are measured by mercury penetration and by N2 adsorption. Mercury is forced into the pores under pressure entry into a pore is opposed by surface tension. For example, a pressure of about 71 MPa (700 atm) is required to fill a pore with a diameter of 10 nm. The amount of uptake as a function of pressure determines the pore size distribution of the larger pores (44). In complementary experiments, the sizes of the smallest pores (those 1 to 20 nm in diameter) are deterrnined by measurements characterizing desorption of N2 from the catalyst. The basis for the measurement is the capillary condensation that occurs in small pores at pressures less than the vapor pressure of the adsorbed nitrogen. The smaller the diameter of the pore, the greater the lowering of the vapor pressure of the Hquid in it. 

There are two well-established experimental techniques for determining the distribution of pore radii. They are the mercury penetration technique and the desorption isotherm method. 

The mercury penetration approach is based on the fact that liquid mercury has a very high surface tension and the observation that mercury does not wet most catalyst surfaces. This situation holds true for oxide catalysts and supported metal catalysts that make up by far the overwhelming majority of the porous commercial materials of interest. Since mercury does not wet such surfaces, the pressure required to force mercury into the pores will depend on the pore radius. This provides a basis for measuring pore size distributions through measurements of the... 

Brenner, A.M., Adkins, B.D., Spooner, S., and Davis, B.H. 1995. Porosity by small-angle x-ray scattering (SAXS) Comparison with results from mercury penetration and nitrogen adsorption. J. Non-crystal. Solids 185 73-77. 

On porous powdered samples intrusion takes place at low pressures as mercury penetrates the large interparticle voids. Additional intrusion occurs at higher pressures into pores within the particles. 

H. M. Rootare, Advanced E experimental Techniques in Powder Metallurgy, Plenum Press, New York, 1970, pp. 225—252. A comprehensive review of the use of mercury penetration to measure porosity. 

An alternative explanation of the data presented in Figure 3 is that the majority of the macropore structure is available for reaction, and by breaking up the coal one is simply opening up hitherto sealed pores. However, this does not seem likely since—to explain the results in Figure 3— one would have to assume that from 2% to 90 mesh the exposed internal area of the coal increases by a factor of 12. Mercury penetration data on Coal C indicates that the macropore area increased only 7% going from 2% to 90 mesh (see Discussions). Also, Malherbe (16) found for three bituminous coals that in going from 5 to 270 mesh the BET area only increased by a factor of 2. Furthermore, the helium density of coal is independent of particle size indicating no sealed pores exist at least in respect to the accessibility of helium (14). 

The only proof of the above contention are the results in Figure 3 of the paper where reaction rate is approximately proportional to external area. Figure A here shows the pore size distribution (from mercury penetration (3)) of each particle size, confirming that little additional pore structure was opened up during coal grinding. This would rule out the possibility that the effect measured in Figure 3 was caused by opening up entrances to sealed pores. 

G. C. Wall and R. J. C. Brown,/. Colloid Interface Sci., 82,141 (1981). The Determination of Pore-Size Distributions from Sorption Isotherms and Mercury Penetration in Interconnected Pores The Application of Percolation Theory. 

The porosity values of bricks lie between 20 and 30 vol.%,391 according to other sources up to 50%.392 According to my own mercury penetration tests, the pore size of bricks lies heavily concentrated around 1 pm.393... 

These mercury penetration tests were performed at the research institute of the VARTA Bat-terie AG in Kelkheim, Germany, in late 1991. 

One problem is that if the silica gel is not very strong, the structure collapses by the external pressure of mercury before pores are penetrated. It is for this reason that the nitrogen adsorption isotherm method is preferred for research purposes. Nevertheless, for strong bodies like industrial catalyst gels, the mercury penetration method is far more rapid not only in execution, but also in converting results to pore size distribution curves. 

Figure 2.9 Mercury penetrating a cylindrical pore taken from ref. (1) with permission.

The penetration of mercury into the pores of a material is a function of applied pressure. At low pressures mercury penetrates the large pores, whereas at higher pressures the smaller pores are progressively filled. Due to the nonwetting nature of mercury on oxide supports, penetration is met with resistance. The Washburn equation relates the pore diameter d with the applied pressure P ... 

The specific surface area was determined by a Micromeritics Model 2200 high-speed, surface-area analyzer using nitrogen as the adsorbate. The pore volume was determined by the mercury penetration method on a Micromeritics Model 900/910 series porosimeter. 

Two Co-Mo-alumina catalysts obtained from a commercial vendor as either marketed or special research samples were used in this study. The surface area and pore-size distributions (using the mercury penetration technique) were determined by an independent commercial laboratory. The catalyst properties are given in Table II. Note that the monodispersed (MD) and bidispersed (BD) catalysts have the same metallic composition and are chemically similar. 

Figure 3, Pore size distribution of mercury penetrable pore volume in calcined Coke A,...

Figure 4 Electron micrograph of DMSO-pretreated human stratum comeum in vitro. Bodd6 and co-workers propose that DMSO increases mercury penetration but does not affect the bimodal distribution visualized in untreated skin. (Reproduced with permission from Ref 46.)...

Figure 3. Mercury penetration into micro-porous particles...

Figure 4. Mercury penetration into an assembly of pellets...

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