Inorganic membranes preparation

Zaspalis and Burggraaf [47] have summarized typical membrane reactor configurations, different membrane/ catalyst combinations, and a large number of membrane reactor studies. Their article clearly shows that inorganic membranes prepared by the sol-gel method, with their dual ability in catalysis and separation, have many unique advantages over other product forms. At the same time, it is important to realize that the parameters which affect a membrane s characteristics and the advantages which the sol-gel process offers are similar to what has been presented thus far. 

Guizard C, Julbe A, and Ayral A. Design of nanosized structures in sol-gel derived porous solids. Application in catalyst and inorganic membranes preparation. J. Mater. Chem. 1999 9 55-65. 

Fig. 7.1. Diagram of the two sol-gel routes used in inorganic membrane preparation.

J. Charpin, P. Bergez, F. Valin, H. Bamier, A. Maurel and J.M. Martinet, Inorganic membranes preparation, characterization, specific applications. Mater. Sci. Monogr., 38C (1987)2211. 

M. Kogure, T. Sato, T. Tanaka, S. Yasujima, T. Suzuki and H. Ohya, Preparation of antimony acid cation exchange membranes by using metal alkoxide-gel method, Bull. Chem. Soc. Jpn., 1991, 1991, 1618 H. Ohya, R. Paterson, T. Nomura, S. McFadzean, T. Suzuki and M. Kogure, Properties of new inorganic membranes prepared by metal alkoxide methods. Part I A new permselective cation exchange membrane based on Si/Ta oxides, J. Membr. Sci., 1995, 105, 103-112. 

H. Ohya, K. Masaoka, M. Aihara and Y. Negishi, Properties of new inorganic membranes prepared by metal alkoxide methods. Part III. New inorganic lithium permselective ion exchange membrane, J. Membr. Sci., 1998,146, 9-13. 

Charpin, J., Bergez, P., Valin, F., Bamier, H., Maurel, A., and Martinet, J. M., Inorganic membranes Preparation, characterization, specific applications. High Tech Ceramics (P. Vincenzini, ed.), Elsevier, Amsterdam, 1987, p. 2211. 

Sforfa ML, Yoshida IVP, Nunes SP (1999) Organic-inorganic membranes prepared Irom polyether diamine and epoxy silane. J Membr Sci 159(1-2) 197-207... 

Application in catalyst and inorganic membranes preparation. J. Mater. Chem. 1999 9 55-65 Guizard C., Julbe A. Nanophase ceramic ion transport membranes for oxygen separation and gas stream enrichment. In Recent Advances in Gas Separation by Microporous Ceramic Membranes, Kanellopoulos N.K., ed., Amsterdam Elsevier, 2000, pp. 435-471 Guizard C., Barboiu M., Bac A., Hovnanian N. Hybrid organic-inorganic membranes with specific transport properties. Applications in separation and sensors technology. Separ. Purif. Technol. 2001 25 167-180... 

Sforca, M.L, Yoshida, I.V.P., and Nunes, S.P. (1999) Oiganic-inorganic membranes prepared from polyether diamine and epoxy silane. /. Memb. ScL, 159,197- 2ff7. 

Sol-gel is one of the most useful techniques for preparation of inorganic membranes with fine pores in the nanometer range (1-5 nm). The sol is a stable suspension of colloidal solid particles within soft uniform solution. The gel was obtained by hydrolysis with open reflux in 24 hours at 85-90 °C. The advantage of sol-gel technology is the ability to produce... 

An inorganic membrane can be prepared by various methods such as sol-gel, phase separation and leaching.2,3 The sol-gel process is considered the most practical method among those used to prepare inorganic membrane. Sol-gel processing is a simple technology in principle but requires considerable effort to become of practical use. The advantage of this... 

For last few years, extensive studies have been carried out on proton conducting inorganic/organic hybrid membranes prepared by sol-gel process for PEMFC operating with either hydrogen or methanol as a fuel [23]. A major motivation for this intense interest on hybrid membranes is high cost, limitation in cell operation temperature, and methanol cross-... 

Although the pyrolysis of organic materials (organic hollow fibers) is used in the commercialization of a new family of inorganic membranes (Fleming 1988) there are only a few descriptions in the open literature. Koresh and Soffer (1980, 1986, 1987) have published a series of articles on this subject. There is also a paper by Bird and Trimm (1983) which is based on a previously described preparation procedure of Trimm and Cooper (1970, 1973). 

Larbot, A., J. A. Alary, C. Guizard, L. Cot and J. Gillot. 1987. New inorganic ultrafiltration membranes Preparation and characterization. Int. J. High Technology Ceramics 3 145-51. 

The separation efficiency (e.g. permselectivity and permeability) of inorganic membranes depends, to a large extent, on the microstructural features of the membrane/support composites such as pore size and its distribution, pore shape, porosity and tortuosity. The microstructures (as a result of the various preparation methods and the processing conditions discussed in Chapter 2) and the membrane/support geometry will be described in some detail, particularly for commercial inorganic membranes. Other material-related membrane properties will be taken into consideration for specific separation applications. For example, the issues of chemical resistance and surface interaction of the membrane material and the physical nature of the module packing materials in relation to the membranes will be addressed. 

Due to their preparation methods, inorganic membranes are in general structurally stable. They do not suffer from any appreciable dimensional instability problems due to compaction and swelling which commonly occur among many organic polymeric membranes. 

Finally, Majda has investigated a novel inorganic membrane-modified electrode [32]. The membrane used was a microporous alumina prepared by anodizing metallic aluminum in an acidic electrolyte [33]. Majda et al. lined the pores of these membranes with polymers and self-assembled monolayers and studied electron and ion transfer down the modified pore walls to a substrate electrode surface [32]. Martin and his coworkers have used the pores in such membranes as templates to prepare nanoscopic metal, polymer, and semiconductor particles [34],... 

Nucleotidases have been studied in liver from various species and activity has been identified in lysosomes, cytoplasmic supernatants and plasma membrane preparations. Arsenis and Touster (31) have purified a 5 -nucleotidase from rat liver lysosomes to apparent homogeneity. The enzyme is unusual in that it hydrolyzes 2 -, 3 -, and 5 -mononucleotides equally well with preference for 5 -dAMP. It also hydrolyzes FMN, p-nitrophenyl phosphate, and /J-glycerol phosphate, but not inorganic pyrophosphate or bis(p-nitrophenyl) phosphate. Unlike the 5 -nucleotidases described thus far, divalent cations such as Co2+, Mn2+, and Mg2+ have no activating effect, but EDTA is inhibitory. In spite of the broad substrate specificity kinetic experiments indicate that a single enzyme is involved. Because of its broad substrate specificity it has been suggested (SI) that it may play a key role in lysosomal catabolism of nucleic acids. 

Different methods have been used to deposit microporous thin films, including solgel, pyrolysis, and deposition techniques [20], Porous inorganic membranes are made of alumina, silica, carbon, zeolites, and other materials [8], They are generally prepared by the slip coating method, the ceramic technique, or the solgel method (Section 3.7). In addition, dense membranes are prepared with metals, oxides, and other materials (Chapter 2). 

To facilitate discussions on the preparation methods, characteristics and applications of inorganic membranes in the following chapters, some terminologies related to the types of membranes according to the combined structures of the separating and support layers, if applicable, will be introduced. 

The methods of preparing inorganic membranes with tortuous pores vary enormously. Some use rigid dense solids as the templates for creating porous structures while many others involve the deposition of one or more layers of smaller pores on a premanufactured microporous support with larger pores. Since ceramic membranes have been studied, produced and commercialized more extensively than any other inorganic membrane materials, more references will be made to the ceramic systems. 

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