Effect of pore volume

The total pore volume of the support is a very iitportant characteristic since this volume equals the total separation volume in SBC (in contrast with, e.g., RPC where the elution volume may be regulated by the corposition of the mobile phase (115)). Yau et al. (108) slxiwed tliat the porosity of tl ]e support is a more important factor affecting the resolution than the pore size distribution of supports with narrow pore size distributions. Traditional media for SEC have pore volumes exceeding 95 % of the laead volume and the high porosity contributes very favourably to ttie resolution of these materials 

The sLf port from Pharmacia AB and e ecially from the Director of Quality Ocsitrol, Mr. Rune Andersson, is gratefully notified. I also thank Leif Ljung of the Biomedical Centre of Uppsala university for skillful assistance in obtaining electron microgr te ty SEM. 

Kirkland and D.D. Bly, Modem Size-Bcclusion Liquid Chromato aphy, Practice of Gel Permeaticxi and Gel Filtration Chromatography, Wil, New York, 1979, pp. 85-91. 

Epton (Ed.), Chromatography of Synthetic and Biological Polymers, Vol. 1, Column Packings, GPC, GF and Gradient Elution, Ellis HOrwood, Chichester, 1978, p. 2. 

Fisher, Laboratory Techniques in Gel Filtration Chjxmatography, Biochemistry and Molecular Biology, T.S. Work and R.H. Burden (Eds.), Elsevier, 1980, pp. 24-61. 

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Figure 12. Effects of Pore Volume on RCCDS Gasoline Yield...

The LPS silica is prepared by extracting the water from a low solids hydrogel with an organic solvent to avoid the compression of aqueous surface tension. This leaves a fragile catalyst of very high pore volume. Such preparations often provide dramatic examples of the effect of pore volume because the same gel dried directly in an oven will frequently be less active or even completely dead. Invariably, nitrogen sorption shows the inactive silica to contain a low pore volume mainly inside small pores, e.g., less than 60 A diameter. In contrast, the active sample dried by extraction usually has equal or greater volume inside small pores, and, in addition, considerable volume... 

In order to evaluate the effect of pore volume blockage in the presence of liquid water causing hindered oxygen transport to the active reaction sites, the direct numerical simulation (DNS) model, mentioned earlier and detailed in our work,25-27 68 is deployed for the pore-scale description of species and charge transport through the reconstructed CL microstructure. 

Figure 25.2 Effect of pore volume on trichloroethene adsorption. (Adapted from Ref. [18].)...

The samples represented in Table 29 provide a good opportunity to test the effect of pore volume independently of surface area. Each sample was activated at 800 °C and tested for ethylene polymerization. All four samples were active, producing polymers having MW that varied with catalyst pore diameter as expected [500]. The melt elasticity also varied, as indicated by the JC-a values listed in the table [521]. As noted in Section 10.4, LCB levels increased when the sample was alkaline aged, regardless of the drying method. However, it is clear from the data in Table 29 that... 

In this case, the "fine" particles and the "coarse" particles were separated so that the difference in size between individual particles was minimized. That is, most of the individual particles in each fraction were almost the same size. Both the fine and coarse particles have a sintering slope of 1/2 but it is the coarse particles which sinter to form a solid having a density closest to theoretical density. This is an excellent example of the effect of pore volume, or void formation, and its effect upon the final density of a solid formed by powder compaction and sintering techniques. Quite obviously, the fine particles give rise to many more voids than the coarser particles so that the attained density of the final sintered solid is much less than for the solid prepared using coarser particles. It is also clear that if one wishes to obtain a sintered product with a density close to the theoretical density, one needs to start with a particle size distribution having particles of varied diameters so that void volume is minimized. 

The uptake of SO2 on activated carbon is related to the degree of its conversion to SO3, which requires the presence of oxygen. It was found that oxidation of sulfur dioxide to sulfur trioxide occurs mainly in the 0.7 nra pores [26, 27]. With an increase in the size of pores in the carbon adsorbents less SO2 is converted, which results in smaller uptake of sulfitr dioxide. The controversial results are reported regarding the effect of pore volume and SO2 uptake in the presence of oxygen. While Bagreev and coworkers reported the importance of porosity [34], Raymundo-Pinero and coworkers could not find any correlation between volume of micropores and the amount of SO2 adsorbed in the presence of oxygen [26]. 

The effects of the concentration of divinylbenzene on pore-size distribution and surface areas of micropores, mesopores, and macropores in monosized PS-DVB beads prepared in the presence of linear polymeric porogens have been studied (65). While the total surface area is clearly determined by the content of divinylbenzene, the sum of pore volumes for mesoforms and macropores, as well as their pore-size distribution, do not change within a broad range of DVB concentrations. However, the more cross-linked the beads, the better the mechanical and hydrodynamic properties. 

The important parameters to consider are the selectivity (dKJdlogR), the ratio of pore volume, Vp, over void volume, Vq, the plate height, H, and the column length, L. The distribution coefficient, Kq, has a slight effect on resolution (with an optimum at Kp 0.3-0.5). In addition to this, extra column effects, such as sample volume, may also contribute to the resolution. 

Pore volume is an indication of the quantity of voids in the catalyst particles and can be a clue in detecting the type of catalyst deactivation that takes place in a commercial unit. Hydrothermal deactivation has very little effect on pore volume, whereas thermal deactivation decreases pore volume. 

A plot called a breakthrough curve shows the effluent liquid concentration c divided by the influent liquid concentration c0 as a function of pore volumes of flow (see Figure 26.11). One pore volume of flow is equal to the volume of the void space in the soil. The effective porosity of the soil is determined by measuring a breakthrough curve. 

The mechanical stability of PSM and AMM-5 samples was investigated by pressing the sample in a die (having a diameter of 16 mm) under different pressures for 15 min. The effects of compression on the surface areas and pore properties of the materials are shown in Table 1. It can be seen that the surface areas of both PSM and AMM-5 samples decrease under high pressure compression. The decrease of surface area, which is proportional to the pressure exerted on the samples, is accompanied with the decrease of pore volume, with no obvious decrease of the pore diameter for both samples. The results indicate that, under high pressure compression, some of the mesoporous channels of MCM-41 have collapsed completely and not constricted to pores of smaller diameter. 

In electrochromatography with porous particles, a (3 factor for the pore volume (Pta) as well as for the interstitial volume (Poul) can be defined. (Note For monolithic or continuous columns, only a single EOF screening factor can be defined for the pore volume.) An important parameter in the discussion of the effects of pore flow on the separation efficiency is the pore-to-interstitial flow ratio (0, which is defined as [18]... 

One effect of pore flow is that it enhances the mass transfer rate between the pore and interstitial volumes. Instead of by molecular diffusion only, which is by nature slow in solution, mass exchange occurs also by perfusive EOF. This effect can be treated as a form of stimulated diffusion. Following the original treatment for pressure-driven LC according to Rodrigues et al. [31], the plate height contribution from stationary-phase mass transfer resistance HCs in the presence of pore flow can be written as... 

Medium Pores (100 A - 1000 A) they have a reasonably high surface area ( 130 m2/cm3 of pore volume), are effective for capture of unvaporized feedstock liquids and display good bottoms cracking with low coke and H2 generation... 

In one experiment, emulsion injection was begun after waterflood, and in the others emulsion injection was begun after tertiary recovery. The number of pore volumes of emulsion injected was 10, 7, and 8, respectively. The reductions in effective permeability, 52, 33, and 56%, were significant, but not as high as those when using oil-free cores. 

Pore size. The pore size distribution of the catalyst matrix plays a key role in the catalytic performance of the catalyst. An optimum pore size distribution usually helps in a balanced distribution of smaller and larger pores, and depends on feedstock type and cracking conditions. The pore size distribution of the matrix changes when another component is added e.g. by adding 35-40% kaolin to a silica-alumina gel, a pore structure with a significant amount of micropores can be obtained. Figure 27.9 Pore volume. Pore volume is an indication of the quantity of voids in the catalyst particles and can be a clue in detecting the type of catalyst deactivation that takes place in a commercial unit. Hydrothermal deactivation has very little effect on pore volume, whereas thermal deactivation decreases pore volume. 

The model correctly describes the permeability reduction as a function of pore volume injected and takes into account the effect of emulsion droplet saturation and droplet-size to pore-size ratios. The main drawbacks of this theory are that the permeability reduction is caused as long as the emulsion is flowing and that the initial permeability is restored once the emulsion injection is followed by water alone. In other words, the emulsion droplets all pass through the porous medium, and none of them is captured inside. However, experimental evidence 9,11) suggests that the permeability reduction cannot be restored after subsequent water injection (Figure 16). 

Figure 9.38. Schematic representation of the response of the chromatographic column for different adsorption isotherms (top). The column breakthrough of a step concentration change without disperson effects is shown (below) for different isotherms (a) linear and (b) convex. The abscissa tItQ is equivalent to the number of pore volumes eluted. (Adapted from Biirgisser et al., 1993.)...

Assessment of the total pore volume liberated shows that thermal treatment of the mesophase up to 120°C does not liberate any porosity. Heating up to 150°C liberates up to 25% of the total porosity whereas only around 50% of the total porosity is liberated when the mesophase was heated up to 300°C. The maximum pore volume is obtained after thermal treatment up to 760°C. When comparing these results with those obtained by SCTA, it would seem that pore blocking occurs. Indeed, after heating to 150°C, with around 25% of the porosity liberated, around 45% of the surfactant is removed. After heating to 300°C, with around 50% of the porosity liberated, up to 70% of the surfactant is removed. We have observed that it is only after treatment to 500°C, with the loss of almost 80% of the total surfactant, that an equivalent amount of pore volume becomes accessible. This pore blocking effect may also explain why the nitrogen desorption isotherms at 77K do not rejoin the adsorption branches at relative pressures below 0.2. 

It is noteworthy that ageing has the same effect on the two kinds of gel (stirred or non stirred) increasing of pore volume, surface and mean diameter, and broadening of the pore range. As a consequence, to avoid these undesirable texture modifications, thermoporometry measurements must be carried out as soon as possible after the preparation of hydrogel samples (within 24 hours). 

The main effect due to a pH decrease is an increase of pore volume and radius. ... 

Catalyst deactivation in hydrodemetallisation (HDM) is caused by the interaction of the metal deposits with the original active phase ( active site poisoning ) and the loss of pore volume due to the obstruction of catalyst pores i pore plugging) (1). However, metal deposits also have an auto-catalytic effect on the hydrodemetallisation reaction, thus active site generation may occur in low active phase loaded or bare support catalyst systems. 

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