Inorganic membranes characterization

The first applications of CMRs have concerned high temperature reactions. The employed inorganic membranes, characterized by higher chemical and thermal stability with respect to polymeric membranes, still today suffer from some important drawbacks high cost, limited lifetime, difficulties in reactor manufacturing (delamination of the membrane top-layer from the support due to the different thermal expansion coefficients). 

H. P. Hsieh, General characteristics of inorganic membranes, in Inorganic Membranes Characterization and Applications, R.R. Bhave (Ed.), van Nostrand Reinhold, New York, 1991. 

Feuillade, V.C. and W.G. Haije, Characterization of Hydrotalcite Materials for C02 Selective Membranes, Proceedings of the 9th International Conference on Inorganic Membranes, Lillehammer, 25-29, June 2006. 

Burggraaf, A.J. and Keizer, K. (1991) Inorganic Membranes Synthesis, Characterization and Applications (ed. 

Fontaine, M.-L., Norby, T., Larring, Y., Grande, T. and Bredesen, R. (2008) in Inorganic Membranes Synthesis, Characterization and Applications (eds R. Mallada and M. Menendez), Elsevier, Amsterdam. 

The preparation and fabrication methods and their conditions described in Chapter 3 dictate the general characteristics of the membranes produced which, in turn, affect their performance as separators or reactors. Physical, chemical and surface properties of inorganic membranes will be described in detail without going into discussions on specific applications which will be treated in later chapters. Therefore, much of this chapter is devoted to characterization techniques and the general characteristics data that they generate. 

Membrane morphology and, in the case of porous membranes, pore size and orientation and porosity are vital to the separation properties of inorganic membranes. As the general characterization techniques evolve, the understanding of these miciostnictures improves. 

Although this technique has been frequently used to characterize microporous organic membranes, it has not been applied to microporous inorganic membranes. Moreover, this method provides only the average pore size but not the pore size distribution. 

The inorganic membrane reactor technology is in a state characterized by very few in practice but many of promise. Since the potential payoff of this technology is enormous, it deserves a close-up look. This and the following three chapters are, therefore, devoted to the review and summary of the various aspects of inorganic membrane reactors applications, material, catalytic and engineering issues. 

In view of the state-of-the-art developments in inorganic membranes, those reactions amenable to inorganic membrane reactors are characterized. The effects of space time in isothermal and non-isothermal membrane reactors are reviewed. 

Gwak, J., Synthesis and characterization of porous inorganic membranes exhibiting specific magnetic properties, Ph.D. dissertation. University Montpellier II, Montpellier, France, 2003. 

Binkerd CR, Ma YH, Moser WR, and Dixon AG. An experimental study of the oxidative coupling of methane in porous ceramic radial-flow catalytic membrane reactors. Proceedings of ICIM4 (Inorganic Membranes), Gatlinburg, TN D.E. Fain (ed.), 1996 441-450. Yeung AKL, Sebastian JM, and Varma A. Mesoporous alumina membranes synthesis, characterization, thermal stability and nonuniform distribution of catalyst. J. Membr. Sci. 1997 131 9-28. 

Sarrade S, Rios GM, and Carles M. Dynamic characterization and transport mechanisms of two inorganic membranes for nanoflltration. 

M.G. Liu, R. Ben Aim and M. Mietton Peuchot, Characterization of inorganic membranes by permporometry method importance of non equilibrium phenomena, in A.J. Burggraaf, J. Charpin and L. Cot (Eds.), Inorganic Membranes. Key Engineering Materials 61 62, Trans Tech Publications, Zurich, 1991, pp. 603-605. 

C.L. Lin, D.L. Flowers and P.K.T. Liu, Characterization of ceramic membranes. II. Modified commercial membranes with pore size imder 40 A. /. Membr. Sci., 92 (1994) 45. J. Luyten, J. Cooymans, R. Persons, R. Leysen and J. Sleurs, A New Ceramic Support Material for Gas Separative Membranes. Paper presented at the 3rd International Conference on Inorganic Membranes, July, 1994, Worcester, MA, USA. 

S. Xiang and Y.H. Ma, Formation and characterization of zeolite membranes from sols. Paper presented at the 3rd International Coivference on Inorganic Membranes, July 10-14,1994, Worcester, MA, USA. 

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. 

A majority of commonly used inorganic membranes are composites consisting of a thin separation barrier on porous support (e.g., Membralox zirconia and alumina membrane products). Inorganic MF and UF membranes are characterized by their narrow pore size distributions. This allows the description of their separative performance in terms of their true pore diameter rather than MW CO value which can vary with operating conditions. This can be advantageous in comparing the relative separation performance of two different membranes independent of the operating conditions. MF membranes, in addition, can be characterized by their bubble point pressures. Due to their superior mechanical resistance bubble point measurements can be extended to smaller diameter MF membranes (0.1 or 0.2 pm) which may have bubble point pressure in excess of 10 bar with water. 

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. 

Basile A, Gallucci F, Tosti S. Synthesis, characterization and applications of palladium membranes. In R. Mallada and M. Mendndez (eds.), Inorganic Membranes Synthesis, Characterization and Applications. Membrane Science and Technology Series, Vol. 13. Elsevier B.V., Amsterdam, The Netherlands, 2008. 

Gallucci F, Tosti S, Basile A (2008) Synthesis, characterization and applications of palladium memlnanes. In Mallada R, Menendez M (eds) Inorganic membranes synthesis, characterization and rqrplications. Chapter 8. Elsevier, Amsterdam (Netherlands)... 

Commercial polymeric membranes are cheap, but very often not sufhciently permselective. For any given gas pair, polymers typically show high selectivities with modest permeabilities, or high permeabilities coupled with reduced selectivities, so that in a selectivity vs. permeability log-log plot aU polymers fall below a so-called upper bound line [1]. On the other hand, inorganic membranes are often very permselective, easy to clean, thermally and chemically resistant, but are usually expensive, brittle, difficult to be prepared in a reproducible way, aud are typically characterized by a low surface-to-volume ratio in modules which, in turn, affects industrial applications (increased dead volume, need of larger compressors) and therefore translates into higher investment and running costs. 

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