Inorganic membrane reactors developments

The other major issue in reactor design concerns catalyst deactivation and membrane fouling. Both contribute to loss of reactor productivity. Development of commercially viable processes using inorganic membrane reactors will only be possible if such barriers are overcome. These subjects will receive greater attention as current R D efforts expand beyond laboratory scale evaluations into field demonstrations. 

Material and catalysis aspects arc the two foremost important factors when considering inorganic membrane reactors. They need to be evaluated early in the development stage. 

Much of the research and development activity on inorganic membrane reactors in recent years has been directed toward hydrogenation or dehydrogenation of hydrocarbons, especially the latter, and other reactions involving production or depletion of hydrogen. This can be attributed to a number of factors. 

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. 

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. 

Tennison S. Current hurdles in the commercial development of inorganic membrane reactors. Membr. Technol. 2000 128 4-9. 

Ilias and Govind(lO) have reviewed the development of high temperature membranes lor membrane reactor application. Hsieh(4) has summarized the technology in the area of important inorganic membranes, the thermal and mechanical stabilities of these membranes, selective permeabilities, catalyst impregnation, membrane/reaction considerations, reactor configuration, and reaction coupling. 

Despite their potential advantages over organic membranes because of their inherent stabilities, inorganic membranes as separators and reactors at the current stage of development are subject to several material, catalysis and engineering limitations. Those limitations which will be treated in more detail in subsequent chapters are more a reflection of the early stage of developments than practical or theoretical limits. It is expected that more interest and demonstrated feasibilities will motivate more focused development efforts to address those issues. 

Finally, the current status of the inorganic membrane technology is summarized for an overall perspective. The future is speculated based on that perspective to provide a framework for future developments in the synthesis, fabrication and assembly of inorganic membranes and their uses for traditional liquid-phase separation, high-temperature gas separation and membrane reactor applications. 

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