Ceramic Membrane Materials

Ceramic membranes may overcome some of the disadvantages of polymeric membranes, particularly the chemical resistance. The higher cost of ceramic membranes may be compensated by the significantly higher fluxes, especially at high temperatures. A full comparison of polymeric and ceramic membranes is given in Table 3.3. 

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]. 

A-type zeolite pervaporation membranes have been developed by Mitsui Engineering Shipbuilding Co Ltd, which have been implemented in an industrial 

Low production cost Production upscaling easy Variation in module form easy Stability at long term unknown Limited versatility in organics Vulnerable for unknown components in mixtures 

Thermal regeneration impossible High-temperature applications impossible 

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The vast increase in the application of membranes has expanded our knowledge of fabrication of various types of membrane, such as organic and inorganic membranes. The inorganic membrane is frequently called a ceramic membrane. To fulfil the need of the market, ceramic membranes represent a distinct class of inorganic membrane. There are a few important parameters involved in ceramic membrane materials, in terms of porous structure, chemical composition and shape of the filter in use. In this research, zirconia-coated y-alumina membranes have been developed using the sol-gel technique. 

The issue of chemical resistance Is relevant not only during applications but also in membrane cleaning procedures which often specify strong acids and bases and sometimes peroxides. Moreover, nonoxidc ceramic membrane materials are prone to reaction upon extended exposure to oxidizing environments. 

Even within a given metal oxide, the chemical resistance varies with the particular phase. Consider the most commonly used ceramic membrane material alumina. The... 

Non-oxide ceramic materials such as silicon carbide has been used commercially as a membrane support material and studied as a potential membrane material. Silicon nitride has also the potential of being a ceramic membrane material. In fact, both materials have been used in other high-temperature structural ceramic applications. Oxidation resistance of these non-oxide ceramics as membrane materials for membrane reactor applications is obviously very important. The oxidation rate is related to the reactive surface area thus oxidation of porous non-oxide ceramics depends on their open porosity. The generally accepted oxidation mechanism of porous silicon nitride materials consists of two... 

In order to develop a ceramic membrane material for a hydrogen separation, experimental efforts are being made. The development of an adsorbent for a separation of oxygen from the SO3-SO2-O2 mixture will be initiated in 2006. 

Moritz, T. et al.. Investigation of ceramic membrane materials by streaming potential measurements. Colloids Surf. A, 195, 25, 2001. 

This chapter focuses on the chemical processing of ceramic membranes, which has to date constituted the major part of inorganic membrane development. Before going further into the ceramic aspect, it is important to understand the requirements for ceramic membrane materials in terms of porous structure, chemical composition, and shape. In separation technologies based on permselective membranes, the difference in filtered species ranges from micrometer-sized particles to nanometer-sized species, such as molecular solutes or gas molecules. One can see that the connected porosity of the membrane must be adapted to the class of products to be separated. For this reason, ceramic membrane manufacture is concerned with macropores above 0.1 pm in diameter for microfiltration, mesopores ranging from 0.1 pm to 2 nm for ultrafiltration, and nanopores less than 2 nm in diameter for nanofiltration, per-vaporation, or gas separation. Dense membranes are also of interest for gas... 

Tong, J., Yang, W., Zhu, B. and Cai, R. (2002) Investigation of ideal zirconium-doped perovskite-type ceramic membrane materials for oxygen separation. Journal of Membrane Science, 203, 175. 

Lin Y S and Zheng Y (1996), Catalytic properties of oxygen semipermeable perovskite-type ceramic membrane materials for oxidative coupling of methane ,/ Catal, 164,220-231. 

Investigation of ideal zirconium-doped perovskite-type ceramic membrane materials for oxygen separation. /. Membr. 

Pecanac, G., Foghmoes, S., Lipinska-Chwalek, M., Baumann, S., Beck, T., and Malzbender, J. (2013) Strength degradation and iailure limits of dense and porous ceramic membrane materials. /. Eur. Ceram. Soc., 33, 2689-2698. 

In practice, the majority of the physisorption isotherms can be divided into six groups (Sing et al, 1985) as shown in Rg. 8.14, each of which has characteristic pore size regimes and pore surface energies. There is a plethora of literature reviews, book chapters and entire books (Do, 1998) dedicated to the understanding of adsorption analysis and as such a full discussion is outside the scope of this chapter. However, the most important isotherms for porous ceramic membrane materials are type I, which corresponds to microporous solids, and types TV and V, which are characteristic of mes-oporous solids (especially ceramics) undergoing capillary condensation and hysteresis during desorption. 

Despite its widespread usage and relatively well-understood analysis techniques, the use of adsorption/desorption isotherms to characterise porous ceramic membrane materials is not without its drawbacks. Firstly,... 

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