Hollow fiber silica

Ono Y, kanekiyo Y, Inoue K, Hojo J, Shinkai S (1999) Evidence for the Importance of a cationic charge in the formation of hollow fiber silica from an organic gel system. Chem Lett 28 23-24... 

On the contrary, silica membranes with pore diameters in the 0.3-0.8 nm on porous glass supports have been claimed to exhibit an H2/CO separation factor as high as 30. This is significantly higher than what Knudsen diffusion alone predicts. It is possible that some molecular sieving takes place in the reportedly small pores in the silica membranes. This postulation appears to be further reinforced by another study using hollow fiber silica... 

Ono, Y., Nakashima, K., Sano, M, Kanekiyo, Y., Inoue, K., Hojo, J. and Shinkai, S., 1998, Organic gels are useful as a template for the preparation of hollow fiber silica. Chemical Communications, 1998 1477-1478. 

M. Hassan, J.D. Way, P.M. Thoen and A.C. Dillon, Separation of gas mixtures using hollow fiber silica membranes, in Y.H. Ma (Ed.), Proceedings of 3rd International Conference on Inorganic Membranes (ICIM3), July 10-14,1994, Worcester, MA, USA. Distributed by Worcester Polytechnic Institute, 100 Institute Rd. Worcester, MA 01609, USA. pp. 325-335. 

For the cholesterol derivatives 22 and 23 the transcription into hollow fiber silica occurred even in the absence of metal salt additives. This phenomenon was ascribed to the protonation of the monoaza- and diaza-18-crown-6 moieties due to their relatively high pA a values, thus providing under the sol-gel polymerization conditions the required cationic charges for the stimulation of the transcription effect. 

This concept called sol-gel transcription can be apphed to a porphyrin-based organogel system of 3 [39]. The slow speed of the bundle formation of 3 in D ME/alcohol provided a greater chance to transcribe nano-sized incipient fibers into silica. Gelator 3 aggregates unimolecularly into a onedimensional stack, along which sol-gel polycondensation of TEOS proceeds in the gel phase. The formed hollow fiber silica has a nearly monodispersed hollow size with 4-5 nm inner diameters, which is comparable to the mo-... 

Figure 6.1. Permeability of several gases through a silica based hollow fiber membrane data taken from Shindo et al. (1983).

Hollow fibers have been tried as liquid-core fibers in spectrophotometry [118] and porous fibers have been well adapted for gas measurements [119,120]. The latter are made of porous polymers, which can trap indicators or reagents in the matrix with a very high permeability of gases and liquids. For liquid applications, porous silica gel has also been used [121],... 

Q, S, and E) Fractoflow, Chromolith Merck (Germany) Hollow fibers, monolithic rods Polyamide, silica lEX, RP... 

Many researchers have assessed the effect of pulsatile flow on different membrane processes with wide range of feeds. One of the first studies was by Kennedy et al. [48] who showed that flux in the RO of sucrose solution could increase by 70% by pulsatile flow at 1 Hz. Gupta et al. [49] reported a 45% enhancement of flux in MF of raw apple juice with a pressure waveform provided by a fast piston return followed by a fast forward stroke at 1 Hz. Jaffrin [50], using hollow fiber filters, demonstrated a 45% enhancement in flux in plasma filtration. Using the collapsible-tube oscillation generator described above, Bertram et al. [47] demonstrated that pulsation resulted in a 60% increase in permeate flux in the filtration of silica suspensions. 

The polymer-coated hollow-fibers employ a silica-glass capillary tube as the substrate. Since the wall of the glass is thinner than 40 pm, it is highly flexible, and the minimum bending radius is less than 5 mm for a 320-pm-bore glass tube. 

C)110 1, BrCN-Sepharose 1011, silica gel11021, or in a hollow fiber ultrafiltration membrane [421. The Eupergit C immobilized pig liver esterase retains 68% of the specific activity of the soluble enzyme. It is easily removed by filtration from the reaction mixture and can be reused several times when stored at 7 °C. In large-scale experiments with pig liver esterase in aqueous solution the enzyme can be stabilized, if necessary, by the addition of inexpensive bovine serum albumin1411. For a determination of the ee value of the monoester, different methods can be used ... 

The formation of hierarchical pore structures in the silica has also been achieved by the use of a gelator 2,3-di- -decyloxyanthracene in methanol [61]. Hollow fibers with micron-sized diameters are obtained on removal of the gelator, which contain mesopores from smaUer gelator aggregates. Changes in the mesopore diameter (5-12 nm) and shape (ink-bottle or cyHndrical) occur for different gelator concentrations. 

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