Vycor glass membranes

Kameyama, T., K. Fukuda and M. Dokiya. 1981. Possibility for effective production of hydrogen from hydrogen sulfide by means of a porous Vycor glass membrane. Ind. Eng. Chem. Fundam. 20 97-99. 

Decomposition of Hydrogen Sulfide Porous ir-AljOj/MoSj membranes Porous Y-AI2O3 membranes Porous Vycor glass membranes Abe (1987) Kameyama et al. (1981) Kameyama et al. (1979, 1981a, b)... 

Decomposition of Hydrogen Iodide Porous Vycor glass membranes Nonporous Pd/Ag membranes Itoh et al (1984) Yeheskel, Leger and Courvoisier (1979)... 

Dehydrogenation of Cyclohexane to Benzene Porous AljOj membranes Porous Vycor glass membranes Nonporous Pd/Ag membranes Fleming (1987) Shinji et al. (1982), Itoh (1987, Itoh et al. 1988) Sun and Khang (1988) Wood (1968), Itoh (1987), Gryaznov (1970)... 

In general, the Vycor glass membrane can be considered to be a membrane of the Knudsen type. Thus, the selectivity of transport of two gases i and j is approximately related to their molecular weights [27] according to ... 

It is clear that the cyclohexane conversion increases with an increasing sweep ratio y- that is, with increasing driving forces for mass transfer through the membrane. In addition, the introduction of a more diluted feed leads to an enhanced conversion. Proof of an effect of the realized product removal via the Vycor glass membrane was the fact that the achieved conversions exceeded the equilibrium conversions (shown as dotted fines in Fig. 12.10). 

T. Kameyama, M. Dokiya, M. Fujishige, H. Yokokawa and K. Fukuda, Possibility for Effective Production of Hydrogen from Hydrogen Sulfide by Means of a Porous Vycor Glass Membrane , Ind. Eng. Chem. Fu-nam., 20 97-99 (1981). 

The above-mentioned results on metal and Vycor glass membranes made us believe that the membranes which are developed for steam-reforming conditions, as described in this thesis, might be used as a starting point for developing a Th-permselective a H2S dehydrogenation membrane reactor. 

Most porous membranes used in CMRs are made from oxide materials, although carbon membranes have also been used [1, 14, 22], However, although they possess very good separative properties, they have received less attention in CMR applications, probably due to their limited resistance to oxidative atmospheres. Vycor glass membranes also have certain drawbacks (brittleness, lack of high-temperature resistance) [9] for use in CMRs. Porous membranes in CMRs are, most often, made from ceramic materials or, more recently, from zeolites. 

Figure 5. AFM image of Vycor glass membrane showing pore mouths about 4 nm wide. Reprinted with permission from ref. 48. Copyright 2001 Kluwer Academic Publishers.

A porous Vycor glass membrane and a porous gamma-alumina membrane, both having about the same pore diameter of 4 nm, were used to study the separation of hydrogen from other components in the gasification mixture [McMahon et al., 1990]. At a temperature up to a maximum hydrogen concentration of about 40% in the... 

Figure 9.2 Calculated total conversion profile of cyclohexane to benzene in a porous shell-and-tube Vycor glass membrane reactor with membrane thickness as a parameter [ltohetal.,1985]...

Exposures of some metal oxide membranes, both dense and porous, to extreme pH conditions (e.g., pH less than 2 or greater than 12) can cause structural degradations, particularly with extended contact time. The extent of degradation depends on the specific phase of the material, porosity, and temperature. Steam can also be deleterious to some metal oxide and Vycor glass membranes. For example, as mentioned earlier, porous glass membranes undergo slow structural changes upon exposure to water due to partial dissolution of silica. 

Figure 10.10 Effect of space time on conversion of partial oxidation of methanol in a porous Vycor glass membrane reactor (350 C, 60% air) [Song and Hwang, 1991]...

Ethylbenzene dehydro-genalion/Vycor glass membrane, noncatalytic... 

Shindo Y, Obata K., Hakuta T., Yoshitome H., Todo N. and Kato J., Permeation of hydrogen through a porous vycor glass membrane, Adv. Hydrogen Energy Progr, 2 325 (1981). 

Harold M.P., Cini P, Patenaude B. and Venkataraman K., The catalytically impregnated ceramic tube An alternative multiphase reactor, AIChE Symposium Series 85 (265) 26 (1989). Song J.Y. and Hwang S.-T, Formaldehyde production from methanol using a porous Vycor glass membrane. Proceedings of ICOM 90, Chicago, (30)540 (1990). 

Experimental data from the literature [15] concerning freon 113 permeability on a vycor glass membrane were simulated by the 3D network model. An average effective length of each pore was selected in a way that the (non-condensing) helium permeability predicted by the network matches the experimental values, and at the same time gives a porosity and surface area close to the experimental ones. Subsequently, the pore size distribution obtained from porosimetry and the effective pore length were used for the simulation of the condensable vapor permeability. 

Figure 5. Comparison of network (solid lines) and experimental results [19] of Freon 113 permeability on Vycor glass membrane...

Similar maxima have been found by Rhim and Hwang [36] for C2H6, n-bu-tane and CO2 in Vycor glass membranes and by Uhlhorn et al. [37] for propylene at 263 K in y-alumina membranes(pore diameter of about 3 nm) as shown in Fig. 9.10. 

Okubo et al. [40,41] treated Vycor glass membranes with tetra-ethoxysilane which was initially adsorbed and finally decomposed on the pore wall by heat treatment. The pore size was expected to be decreased by this treatment. As a result of this modification the permeation decreased and the permeation as a function of temperature increased (compared with that of the non-modified glass) for the gases He, O2, N2, Ar, H2 and CO2 and became activated. The authors argue that surface diffusion carmot explain this result and suggest that the modified system is in the transition region of Knudsen to molecular sieving (micropore diffusion). 

K.H. Lee and S.T. Hwang, The transport of condeivsable vapors through a microporous Vycor glass membrane. /. Colloid Interface Sci., 110 (1986) 544-555. 

Fig. 11.4. Top figure shows the effect of pressure on the reaction side of the membrane cm methane conversion in the Pd membrane reactor bottom figure shows the effect of temperature. The solid line and the sjmtibols (o) are for the Pd membrane reactor. The dotted line is the calculated equilibrium conversion and the symbols ( ) are for a membrane reactor using a porous Vycor glass membrane. Reproduced from Uemiya et al. [29] with permission.

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