Applications of Inorganic Membranes

Compared with their polymeric coimterparts, inorganic membranes are characterized by high chemical and thermal resistances and high mechanical stability, and thus can be applied in a harsh environment. However, inorganic membranes also exhibit the shortcoming of high cost, because 

Pore size distrihution Mercury porosimetry thermoporometry 

Surface morphology SEM, TEM, atomic force microscopy (AFM), scanning transmission microscopy (STM) 

Mechanical strength Three-point-bending method 

Permeation rate Pure gas or liquid permeation test 

---

Characteristics, technological advances, and future applications of inorganic membranes are discussed in depth. An overview of the origins of these membranes provides a basis for understanding emerging technologies in the field... 

CHEMICAL, SUSTAINABLE ENERGY, AND POLLUTION ABATEMENT APPLICATIONS OF INORGANIC MEMBRANES... 

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. 

Clarification of apple juice. Inorganic membranes have been utilized in two ways in the production of apple juice. One is to clarify pressed or prefiltered apple juice and the other is to extract clarified apple juice directly from apple puree or pomace. Microfiltration of apple juice has been one of the most successful commercial applications of inorganic membranes. 

A number of important applications of inorganic membranes in biotechnology are related to bioreactors for enzymatic and microbial conversion processes. These will be... 

Calcinm glectrowinning in piutniiium production. A potential application of inorganic membranes in radioactive waste treatment is in the industrially practiced direct oxide reduction process. In this process plutonium oxide is calciothermit y reduced to plutonium in the presence of calcium chloride according to the following reaction ... 

The majority of commercial as well as potential applications of inorganic membranes are for pilot or production scale operation. There are, however, limited uses of some inorganic membranes in laboratories. 

Deschamps, A., C. Walther, P. Bergez and J. Charpin, 1989, Application of inorganic membranes in refining processes of petroleum residues, in I. 1st Int Conf. Inorg. Membr., Montpellier, France, p.237. 

Compared to liquid-phase applications, commercial gas- or vapor-phase applications of inorganic membranes have been limited. Due to their low permeabilities, dense inorganic membranes arc utilized only in special and low-volume cases. Hydrogen... 

A major area of potential applications of inorganic membranes is high-tempcrature and/or high-pressure contaminant removal systems to protect process components and to control emissions from advanced coal-based power generation systems. The high temperature and pressure refer to 538 C (lOOO F) and above 5-35 bars, respectively. The potential applications include both bulk separation of gases and the removal of trace... 

Dcllefield. RJ.. High-temperature applications of inorganic membranes. 1988. presented at the Am. Inst Chem. Eng. National Meeting. Denver. CO. USA. 

Johnson, H.E., and B.L. Schulman, 1993, Assessment of the potential for refinery applications of inorganic membrane technology an identification and screening analysis, U.S. Department of Energy Final Report under Contract No. DE-ACOl-88FE61680(Task 23). 

Despite the unique properties of inorganic membranes vs. the rather well-established polymeric ones (see Table 1 for a comparison), issues such as membrane instability, insufficient permeability or permselectivity, or simply the unbearable costs implied still hamper the application of inorganic-membrane reactors in the process industry. 

However, at least for separative applications, most hopes to find consistent application of inorganic-membrane reactors lie in the development of inorganic membranes having pores of molecular dimensions (<10 A, e.g., zeolitic membranes). Such membranes should moreover be thin enough to allow reasonable permeability, defect-free, resilient, and stable from the thermal, mechanical, and chemical standpoints. Such results should not be achieved only at a lab scale (a lot of promising literature has recently appeared in this context), but should also be reproducible at a large, industrial scale. Last, but not least, such membranes should not be unacceptably expensive, in both their initial and their replacement costs. 

FIGURE 10.21 (See color insert following page 588.) Traditional applications of inorganic membrane reactors for (a) conversion enhancement by product removal, (b) permeation of products and reaction coupling, and (c) selectivity enhancement by reactant distribution. 

Trowbridge, L.D. Application of inorganic membrane technology to hydrogen-hydrocarbon separations. ORNL/TM-2003/139, June 2003. 

Besides the application of inorganic membranes in stand-alone gas separation units, attention is focused on more process-integrated applications. In such configurations the separation hmction of the membrane can be used to shift the equilibrium of a chemical reaction by selective removal of one or more components on the product side of the reaction in a so-Ccdled membrane reactor. 

H.E. Johnson and B.L. Schulman, Assessment of the Potential for Refinery Applications of Inorganic Membrane Technology — An Identification and Screening Analysis. DOE/FE-61680-H3, Final report. May 1993. 

Some limitations of inorganic ceramic membranes are its sensitivity to mechanical impact, vibration, temperatme, and pressure variations pore size, which is limited only to UF and MF applications need of high-capacity pump to obtain the recommended speed flow of 2-6 m s" and finally, high cost, which probably represents the main limitation to the application of inorganic membranes [6]. 

Membrane Processes in Separation and Purification published in 1993, contains chapters on pervaporation, facilitated transport membrane processes, membrane gas absorption processes, hollow fiber contactors, membrane reactors, and the preparation and application of inorganic membranes. In addition to an introductory chapter by the editors. Polymeric... 

Cot, L., Guizard, C., Julbe, A., and Larbot. A., Preparation and Application of Inorganic Membranes, in Membrane Processes in Separation and Purification, Eds. Crespo, J.G. and Boddeker, K.W., Kluwer Academic Publishers, Dordrecht, The Netherlands, 1994. 

---