Ceramic pervaporation membranes

Some efforts have already been made to develop ceramic pervaporation membranes, especially silica and zeolite membranes, which are both hydrophilic membranes. Silica pervaporation membranes have been developed by ECN, The Netherlands. The membranes were tested in a pilot installation of 1 m2 membrane surface at Akzo Nobel and other companies in the Netherlands [34, 35]. 

Table 3.3 Comparison of polymeric and ceramic pervaporation membranes.

J.W. Bakker, Application of Ceramic Pervaporation Membranes in Polycondensation Reactions , pp. 448-51 in Proc. ICIM5 June 22-28, Nagoya, Japan (1998). 

Although low molecular weight esterifications (and etherifications) can benefit substantially from an integration with pervaporation, to our knowledge no large-scale applications have emerged so far. Probably closer to final application is the development by Akzo Nobel on the application of ceramic pervaporation membranes in polycondensation reactions [99, 100]. In the production of alkyd coating... 

Peters, T.A., Benes, N.E. and Keurentjes, J.T.F. 2005a. Zeolite-coated ceramic pervaporation membranes pervaporation-esterification coupling and reactor evaluation. 

Fig. 6.8 Setup used for the carboxylation of ethanol in single phase sc-conditions, using a flow reactor and an inorganic ceramic pervaporation membrane for water separation. Reprinted with permission from [60]. Copyright (2012) John Wiley and Sons...

Y. Zhu, R.G. Minet and T.T. Tsotsis, A Continuous Pervaporation Membrane Reactor for the Study of Esterification Reactions Using a Composite Polymeric/Ceramic Membrane, Chem. Eng. Sci. 51, 4103 (1996). 

Similar trends are developing for ceramic membranes applied in pervaporation and nanofiltration, although much slower because ceramic pervaporation and nanofiltration membranes are still sparsely available more experimental observations and experience with applications are needed in this field. Promising results were obtained by Sekulic et al. [61] for titania membranes that can be used in pervaporation as well as nanofiltration. 

Pervaporation with ceramic membranes is less well understood in terms of transport mechanisms. Consequently, modeling of ceramic pervaporation is still less mature, although the performance of the process was reported to be good [89]. Nomura et al. [90] studied the transport mechanism of ethanol/water through silicalite membranes in... 

Problems to be solved are related to membrane stability (of polymeric membranes, but also the development of hydrophobic ceramic nanofiltration membranes and pervaporation membranes resistant to extreme conditions), to a lack of fundamental knowledge on transport mechanisms and models, and to the need for simulation tools to be able to predict the performance of solvent-resistant nanofiltration and pervaporation in a process environment. This will require an investment in basic and applied research, but will generate a breakthrough in important societal issues such as energy consumption, global warming and the development of a sustainable chemical industry. 

Zhu Y, Minet RG, and Tsotsis TT. A continuous pervaporation membrane reactor for the study of esterification reactions using a composite polymeric/ceramic membrane. Chem Eng Sci 1996 5(17) 4103-4113. 

In the middle of the last century, the original form of zeolite membranes were synthesized by dispersing the zeolite crystals in polymer membrane matrixes, which were used for gas separation and pervaporative alcohol/water separations. In the last few decades, the researches of polycrystalline zeolite membranes that supported on ceramic, glass, or metal substrates have grown into an attractive and abundant field. Their applications for gas separation, pervaporation, membrane reactors, sensors, low-k films, corrosion protection coatings, zeolite modified electrodes, fuel cells, heat pumps et al. have been wildly explored. In the following text, the applications of supported polycrystalline zeolite membranes for energy and fuels will be presented. 

Gongping L, Wang W, Wanqin J, Nanping X. 2012. Polymer/ ceramic composite membranes and their application in pervaporation process. Chin. J. Chem. Eng. 20(1) 62—70. 

Xu R, Liu G, Dong X, Jin W. 2010. Pervaporation separation of n-octane/thiophene mixtures using polydimethylsUoxane/ ceramic composite membranes. Desalination 258 106-111. 

Wang Z, Qinqin G, Shao J, Yan Y. High performance zeolite LTA pervaporation membranes on ceramic hollow fibers by dipcoating-wiping seed deposition. J Am Chem Soc 2009 131 6910-6911. 

Both polymer and ceramic membranes are applied in pervaporation-based reactors, for which Fig. 5.9 shows the two basic configurations [108]. Table 5.2 gives an overview of the performance of various pervaporation membranes and Tab. 5.3 shows some examples of membrane-assisted esterification reactions. In addition to these low molecular weight esters, pervaporation can also be used for the production of polycondensation esters (resins) [99, 100]. 

With pervaporation membranes the water can be removed during the condensation reaction. In this case, a tubular microporous ceramic membrane supplied by ECN [124] was used. The separating layer of this membrane consists of a less than 0.5 mm film of microporous amorphous silica on the outside of a multilayer alumina support. The average pore size of this layer is 0.3-0.4 nm. After addition of the reactants, the reactor is heated to the desired temperature, the recyde of the mixture over the outside of the membrane tubes is started and a vacuum is apphed at the permeate side. In some cases a sweep gas can also be used. The pressure inside the reactor is a function of the partial vapor pressures and the reaction mixture is non-boiling. Although it can be anticipated that concentration polarization will play an important role in these systems, computational fluid dynamics calculations have shown that the membrane surface is effectively refreshed as a result of buoyancy effects [125]. 

Cohen, Y. 2002. Ceramic-supported polymer (CSP) pervaporation membrane. US 6440309. 

Peters, T.A., Poeth, C.H.S., Benes, N.E., Buijs, H.C.W.M., Vercauteren, F.F. and Keurentjes, J.T.F. 2006. Ceramic-supported thin PVA pervaporation membranes combining high flux and high selectivity contradicting the flux-selectivity paradigm. J. Memb. Sci. 276(1-2) 42-50. 

Since the lower limit for preparing porous membranes by sintering is about 0.1 pm in pore diameter, this technique cannot be used to prepare ultrafiltration membranes. Such sintered porous structures can be used as the sublayer for composite ultrafiltration membranes, a technique frequently employed in the preparation of the ceramic ultrafiltration membranes. On the other band, ultrafiltration membranes themselves are often used as sublayers in composite membranes for reverse osmosis, nanofiltcation, gas separation and pervaporation. - -... 

Cuperus F.P., van Gemert R.W. Dehydration using ceramic silica pervaporation membranes the influence of hydrodynamic conditions. Separ. Purif. Technol. 2002 27 225-229 Dalmon J.A. Catalytic membrane reactors. In Handbook of Heterogeneous Catalysis, Ertl G., Knbzinger H., Weitkamp J., eds. VCH Publication, 1997, Chapter 9.3 DeFriend K.A., Barron A.R. A simple approach to hierarchical ceramic ultrafiltration membranes. J. Membr. Sci. 2003 212 29-38... 

G. Liu, F. Xiangh, W. Wei, S. Liu, W. Jin, Improved performance of PDMS/ceramic composite pervaporation membranes by ZSM-5 homogeneously dispersed in PDMS via a surface graft/coating approach. Chemical Engineering Journal 174 (2011) 495-503. 

Both Mitsui [26] and Sulzer [27] have commercialized these membranes for dehydration of alcohols by pervaporation or vapor/vapor permeation. The membranes are made in tubular form. Extraordinarily high selectivities have been reported for these membranes, and their ceramic nature allows operation at high temperatures, so fluxes are high. These advantages are, however, offset by the costs of the membrane modules, currently in excess of US 3000/m2 of membrane. 

M. Asaeda, Preparation of thin Porous Sihca Membranes for Separation of Non-Aqueous Organic Solvent Mixtures by Pervaporation , Ceram. Trans., 31 411-20 (1993). 

FIGURE 6.27 General working principle of a pervaporation or vapor permeation module equipped with tubular ceramic membrane elements. 

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