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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Studies in the past 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 significantly reduced time for the fabrication of zeolites employing microwave energy. However, the mechanism and engineering for the enhanced rates of syntheses are unknown. The results from different laboratories are not consistent, and experimental details are sparse. We studied the synthesis of silicalite employing two geometries in an oven with 2.45-GHz microwaves. The distribution of microwave energies within the reactors from simulation differed, and the morphologies and yields of the resultant zeolite also differed. Larger uniform silicalite crystals were formed in the larger reactor in which the variation in microwave energy distribution was greater. Engineering the energy distribution within a microwave synthesis reactor is necessary to understand and control the process.

The influence of microwa®e radiation on adsorption selecti®ity was studied using the adsorption and desorption of cyclohexane and methanol on high-silica zeolites.

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