Liquid impregnation pore filling

Two cases can be distinguished, depending on whether the pore space of the support contains only ambient air at the start or whether it is already filled by the solvent from the impregnation solution (usually water) or by another liquid. Impregnation is said to be capillary in the former case and diffusional in the latter. 

Figure 11, Schematic mechanisms of pore filling and pore blocking by liquid impregnation and by chemical vapor deposition (26).

Figure 14.5 Schematic mechanisms of pore filling and pore blocking by liquid impregnation and by chemical vapor deposition. Source Reprinted with permission from Kollensky WV, Chem Phys Carbon, 9, 173, 1973. Copyright 1973, CRC Press, Boca Raton, Florida.

As long as the regions filled with the liquid are present as a continuous network up to the external surface, the system is said to be in the funicular state. When the continuous network of liquid elements breaks up, the system is said to be in the pendular state. Now, the rate is completely determined by transport of vapor through the emptied pores of the solid. Because the fraction of the pores filled with liquid shrinks to the center of the impregnated body, the rate of evaporation drops more rapidly. 

Pores filling with ionic liquid by direct immersion of the PBI support into the molten ionic liquid at 50°C introduced the membrane proton conductivity. After impregnation the proton conductivity of this PBI ionic liquid membrane reached a value of 1.86 mS cnT at 190°C. 

To improve the filling of the pores of the alumina layer with impregnation liquid, the samples are evacuated in an exsiccator and conditioned with carbon dioxide... 

Impregnation. A porous product can be dipped into a fluid reactive liquid, which soaks into the pores and fills them completely. The liquid is then cured to leave the product completely filled with solid polymer in the pores. 

The technique consists in measuring the B (e.g. water) flow rate (/) through a membrane impregnated with A (e.g. isobutanol or mixtures of alcohols and water) as a function of the pressure difference AP. We have to note that it is possible to modify the method from "pressure controlled" to "flow controlled" in order to reduce the test time and increase its flexibility [126]. At a certain minimum pressure the largest pores become permeable, while the smaller pores still remain impermeable. This minimum pressure depends mainly on the type of membrane material (contact angle), type of permeate (surface tension) and pore size. When all pores are filled with B, the liquid flux / through the membrane becomes directly proportional to the pressure. 

In Chapter 2 we discussed a number of studies with three-phase catalytic membrane reactors. In these reactors the catalyst is impregnated within the membrane, which serves as a contactor between the gas phase (B) and liquid phase reactants (A), and the catalyst that resides within the membrane pores. When gas/liquid reactions occur in conventional (packed, -trickle or fluidized-bed) multiphase catalytic reactors the solid catalyst is wetted by a liquid film as a result, the gas, before reaching the catalyst particle surface or pore, has to diffuse through the liquid layer, which acts as an additional mass transfer resistance between the gas and the solid. In the case of a catalytic membrane reactor, as shown schematically in Fig. 5.16, the active membrane pores are filled simultaneously with the liquid and gas reactants, ensuring an effective contact between the three phases (gas/ liquid, and catalyst). One of the earliest studies of this type of reactor was reported by Akyurtlu et al [5.58], who developed a semi-analytical model coupling analytical results with a numerical solution for this type of reactor. Harold and coworkers (Harold and Ng... 

Hydrated cellulose (viscous) fibers, unwoven materials (e.g. felt), with different fiber interweaving and chemical reagents of high purity were used. Hydrated cellulose was chosen as a polymer precursor. Its structure is a complex system composed of micro-fibrils and micro- and macropores and also of a branched network of microscopic capillaries. Cellulose has a large inner surface that plays a determining role in absorption of aqueous or organic liquids with polymer molecules. Under the impregnation of hydrated cellulose with aqueous solutions of salts, the liquid fills the space between fibers, pores on the fiber surface and interacts with cellulose macromolecules. 

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