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Studies in the last decade suggest that microwave energy may have a unique ability to influence chemical processes. These include chemical and materials syntheses as well as separations. Specifically, recent studies have documented a significantly reduced time for fabricating zeolites, mixed oxide and mesoporous molecular sieves by employing microwave energy. In many cases, microwave syntheses have proven to synthesize new nanoporous structures. By reducing the times by over an order of magnitude, continuous production would be possible to replace batch synthesis. This lowering of the cost would make more nanoporous materials readily available for many chemical, environmental, and biological applications. Further, microwave syntheses have often proven to create more uniform (defect-free) products than from conventional hydrothermal synthesis. However, the mechanism and engineering for the enhanced rates of syntheses are unknown. We review the many studies that have demonstrated the enhanced syntheses of nanoporous oxides and analyze the proposals to explain differences in microwave reactions. Finally, the microwave reactor engineering is discussed, as it explains the discrepancies between many microwave studies. |
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