Phase inversion packings

If the packing surface is discontinuous in nature, a phase inversion occurs, and gas oubbles through the liquid. The column is not unstable and can be brought back to gas-phase continuous operation by merely reducing the gas rate. Analogously to the flooding condition, the pressure drop rises rapidly as phase inversion occurs. 

Flooding and Loading Since flooding or phase inversion normally represents the maximum capacity condition for a packed column, it is desirable to predict its value for new designs. The first generalized correlation of packed-column flood points was developed by Sherwood, Shipley, and Holloway [Ind. Eng. Chem., 30, 768 (1938)] on the basis of laboratory measurements primarily on the air-water system. 

Of interest here is the question relating to the value for the slope coefficient, k, from equation (1), when surfactant structures incorporating both ionic (say sulphonate) and nonionic moieties are included together. The Ghanges in electric double layer effects imparted from salt addition might dominate the packing constraints and therefore the phase inversion process, or perhaps oxyethylene dehydration effects from the presence of toluene could also play a role. 

Optimal Salinities The phase inversion process may be considered to reflect the balanced nature of the adsorbed surfactant species at the oil/water interface. Simple geometric packing... 

The packing ratio also explains the nature of microemulsion formed by using nonionic surfactants. If v/a 1 increases with increase of temperature (as a result of reduction of a ), one would expect the solubilisation of hydrocarbons in nonionic surfactact to increase with temperature as observed, until v/a l reaches the value of 1 where phase inversion would be expected. At higher temperatures, va l > 1 and water in oil microemulsions would be expected and the solubilisation of water would decrease as the temperature rises again as expected. 

As liquid rates are raised, the liquid occupies some of the cross-section area, making the openings for gas flow smaller. The pressure drop curve will parallel A-B but will be somewhat above it. At high liquid flow rates, the packing voids fill up with frothy liquid. A portion of the energy of the gas is used to support the liquid in the column and pressure drop becomes proportional to the gas rate raised to a power different (usually lower) than 2 (region A -B ). The point where the packing voids fill up, i.e., when tower operation switches from vapor-continuous (normal) to liquid continuous is termed phase inversion. 

Kunz W, Testard F et al (2009) Correspondence between curvature, packing parameter, and hydrophilic-lipophilic deviation scales around the phase-inversion temperature. Langmuir 25 112-115... 

Iversen et al. [6] found that for a polymer strucmre similar to the interstices between closely packed spheres (phase inversion membrane), Equation 38.4 is able to well describe the tortuosity-porosity relationship whereas for a polymer structure similar to random spheres or clusters (stretched membrane), Equation 38.5 has to be used. 

Relative retentions..the a values..usually vary Inversely with column temperature, but are most strongly affected by the choice of liquid phase. In packed column chromatography, the choice of liquid phase Is usually the most effective route by which separation efficiency Is Influenced. In capillary GC, however, there Is normally such an abundance of theoretical plates that the choice of liquid phase Is a relatively unimportant parameter for many analyses. In some cases however. It does become desirable (or even necessary) to select a liquid phase in which the relative retentions of certain solutes Is larger. Until quite recently, this posed a real problem with the fused silica capillary column, because the more polar liquid phases, l.e. those In which relative retentions are usually greater, coated fused silica only reluctantly, and produced columns whose useful lives were quite limited. The development of stable bonded phase columns ( ) eventually overcame this difficulty (vide Infra). 

In Eq 7.8 ( ) is the maximum packing volume fraction, and [q] is the intrinsic viscosity. The computed curves are shown in Figure 7.2. To calculate these dependencies ( ) = 0.8 and [rj] = 2 were assumed. The six points of intersection represent the iso-viscous conditions for the dispersions of liquid 1 in 2 and liquid 2 in 1, or in other words, the conditions for phase inversion. 

Vrc y,y r 11 o - volume fraction of dispersed and matrix phase, respectively - volume fraction of the crosslinked monomer units - volume fraction of phase i at phase inversion - maximum packing volume fraction - percolation threshold - shear strain and rate of shearing, respectively - viscosity - zero-shear viscosity - hrst and second normal stress difference coefficient, respectively... 

This HPLC procedure uses weak" reversed-phase column packings and inverse-salt gr ents. While it can be consider as a kind of salting out" chromatography, it is also a variation of RPLC 48,49). Retention is related to salt concentration as... 

At about 50% (w/w), phase inversion takes place, and at COP concentrations beyond 50% the formation of LC-rich islands in an LC-poor matrix is observed. These islands have been described by several authors in the COP system [118] and in a blend consisting of a rigid rod and a semiflexible coil polymer [121]. The formation of these islands is mainly due to differences in viscosity and surface tension of LC-poor and LC-rich phases and the tendency to achieve efficient packing by orientation and the lowering of lateral distances of the anisotropic parts of a polymer. The LC-poor (= PC-rich) matrix has a higher melt viscosity than that of COP. In a shear field or under... 

Kleinert et al. [26] studied, for example, POM in a hollow fibre MR. The perovskite membranes used by the authors were produced from Ba(Co,Fe,Zr)03 (BCFZ) powder via phase inversion spinning technique. A tube-in-tube configuration was used while the catalyst was packed in the shell side of the reactor. 

Membranes consisting of the structure depicted schematically in figure V - 5b, i.e. a system of closed packed spheres, can be found in organic and inorganic sintered membranes or in phase inversion"membranes with a nodular top layer structure. Such membranes can best be described by the Kozeny-Carman leladonsMp (eq. V - 56), i.e. 

Asymmetric hollow fiber membranes of polysulfone, polyethersulfone, and polyphenylsulfone can be prepared by phase inversion spinning solvent/nonsolvent dopes, i.e., N-methylpyrrolidone/formamide. These asymmetric hollow fiber membranes possess a microscopically observable skin supported by a porous open cellular network. The walls of the open cells of the matrix are composed of arrays of interconnected spherical micelles. With increasing proximity to the outer surface, the packing density of the spherical micelles increase with a concomitant decline in interstitial porosity. At the outer surface layers, the packing of the micelles becomes... 

Earlier theories of phase inversion were based on packing parameters -inversion occurs when exceeds the maximum packing ( 0.64 for random packing and 0.74 for hexagonal packing of monodisperse spheres for polydisperse... 

Two types of phase inversion may be distinguished (a) Catastrophic, e.g. when the disperse phase volume exceeds its maximum packing and (b) transitional, which occurs over a long period of time due to change in the conditions. An example of transitional phase inversion is when the emulsion is subjected to a temperature change. For example, when an emulsion, prepared using an ethoxylated nonionic... 

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