Interparticle voids

Crushing, selective particle size packing or hydraulic compaction can be used to reduce interparticle void space and increase the bulk density within the storage tank to approach the particle density of the carbon. Even with these extreme methods of packing, the fraction of the vessel which is micropore is never greater than 0.50 for any commercial carbon, considerably short of the 0.70 which is necessary for 170 V/V storage. 

Bulk density is related to particle density through the interparticle void fraction e in the sample. 

Moisture can significantly affect loose materials, particularly their flowability. Low temperatures, particle bridging, and caking can alter interparticle void fractions and cause dramatic changes in bulk density. Moisture becomes bound to solids because of mechanical, physicochemical, and chemical mechanisms. Moisture retained... 

Line-width of XRD peaks of these acidic Cs salts (x = 2.1. 2.2, and 2.5) show that the size of the primary crystallites was about 120 A and the primary crystallites themselves are nonporous [29]. Therefore, the pores observed in the present study correspond to the interparticle voids (not intraparticle). The pore structure and the mechanism of the formation of pores will be discussed in our forthcoming paper. 

The performance of adsorption processes results in general from the combined effects of thermodynamic and rate factors. It is convenient to consider first thermodynamic factors. These determine the process performance in a limit where the system behaves ideally i.e. without mass transfer and kinetic limitations and with the fluid phase in perfect piston flow. Rate factors determine the efficiency of the real process in relation to the ideal process performance. Rate factors include heat-and mass-transfer limitations, reaction kinetic limitations, and hydro-dynamic dispersion resulting from the velocity distribution across the bed and from mixing and diffusion in the interparticle void space. 

The experimental method employed in mercury porosimetry, discussed more extensively in Chapter 20, involves the evacuation of all gas from the volume containing the sample. Mercury is then transferred into the sample container while under vacuum. Finally, pressure is applied to force mercury into the interparticle voids and intraparticle pores. A means of monitoring both the applied pressure and the intruded volume are integral parts of all mercury porosimeters. 

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. 

Figure 11.7 is a cumulative pore-volume intrusion curve which shows the summation of volume intruded into the pores and interparticle voids plotted versus the applied pressure. Recognizing that the increase in interfacial area from equation (10.22) is effectively the pore and void surface area S, this equation can be rewritten as... 

Therefore, the surface area of pores in the range 0.0213-0.00178 m is 235.5 m2 g The area of the large pores and interparticle voids is given by the difference between the total surface area and the area obtained in equation (11.11) or 23.9 m2 g ... 

The onset of thermal diffusion depends on the gas concentrations, the sample surface area, the rate at which the sample cools to bath temperature, and the packing efficiency of the powder. In many instances, using a conventional sample cell, surface areas less than 0.1 m can be accurately measured on well-packed samples that exhibit small interparticle void volume. The use of the micro cell (Fig. 15.10b) is predicated on the latter of these observations. Presumably, by decreasing the available volume into which the lighter gas can settle, the effects of thermal diffusion can be minimized. Although small sample quantities are used with a micro cell, thermal conductivity detectors are sufficiently sensitive to give ample signal. 

Symbol Solid material volume Open pore volume Closed pore volume Interparticle void volume... 

Figure 11.8 Resolution of two elution curves at three theoretical plates, interparticle void fraction = 0.36.

A chromatography column of 10 mm i.d. and 100 mm height was packed with particles for gel chromatography. The interparticle void fraction e was 0.20. A small amount of a protein solution was applied to the column and elution performed in an isocratic manner with a mobile phase at a flow rate of 0.5 cm min. The distribution coefficient A of a protein was 0.7. An elution curve of the Gaussian type was obtained, and the peak width W was 1.30 cm . Calculate the Hs value of this column for this protein sample. 

A 1.0 cm-i.d. and 50 cm-long chromatography column is packed with gel beads that are 100 pm in diameter. The interparticle void fraction e is 0.27, and the flow rate of the mobile phase is 20 cm h. A retention volume of 20 cm and a peak width W of 1.8 cm were obtained for a protein sample. 

Recently various kinds of porous materials have been developed and their properties and structures have been gathering great concerns in science. There are two types of pores of intraparticle pores and interparticle ones[l]. The intraparticle pores are in the primary particle itself, while the interparticle pores originate from the interparticle void spaces. Zeolites are the most representative porous solids whose pores come from the structurally intrinsic intraparticle pores. The pore geometry can be evaluated by their crystallographic data. The carbon nanotube of which pore wall is composed of graphitic sheets is also the... 

The importance of adsorbent non-isothermality during the measurement of sorption kinetics has been recognized in recent years. Several mathematical models to describe the non-isothermal sorption kinetics have been formulated [1-9]. Of particular interest are the models describing the uptake during a differential sorption test because they provide relatively simple analytical solutions for data analysis [6-9]. These models assume that mass transfer can be described by the Fickian diffusion model and heat transfer from the solid is controlled by a film resistance outside the adsorbent particle. Diffusion of adsorbed molecules inside the adsorbent and gas diffusion in the interparticle voids have been considered as the controlling mechanism for mass transfer. 

Initial viscosities seem to be dependent on several resin variables within the plastisol. Resin particle size distribution is important to the viscosity in that decreased interparticle void volume by improved packing will decrease plastisol viscosities. The intraparticle void volume within agglo-... 

Bulk density, or packing density, includes all pores and voids (interparticle spaces) in its calculation. It is determined by filling a graduated cylinder, with or without tapping. It follows that the value obtained is dependent upon the form of the catalyst (powder, tablets, extrudates) because of the different contribution of interparticle void space to the pore volume. Tap density is the apparent density of a bed of particles in a container of stated dimensions when a given amount of powder is vibrated or tapped under controlled conditions. The use of the term bulk density should be... 

For the separation of the loaded zeolite from the product suspension, centrifugation can be used. The interparticle void volume of zeolite consists of a solution that contains the substrates and fructose as a byproduct. Therefore several washing steps are required. The more washing effort applied, the higher the resulting purity of isomaltose (Fig. 16). However, a rise in isomaltose purity comes along with lower product yields. 

If there is little deformation, much higher forces can result. At the veiy highest forces, the particles rupture, creating smaller particles which fill the interparticle voids between other particles and fiuiher increase the density of the powder. 

The total amounts of adsorbate adsorbed show no large differences near saturation pressure at Pq = 73.3 hPa. All three samples base on fumed silica of surface area SA = 300 m g referring to a hydrophilic surface. In the high-pressure, multilayer and capillary condensation region the adsorption isotherm is dominated by particle size and aggregate interparticle voids in the mesopore range. But in the low-pressure submonolayer region of the isotherm at p p < 0.07, the adsorbate uptake is controlled by... 

---