Advantages of Microwave Synthesis

Microwave synthesis offers a large range of advantages over conventional synthesis. The consequences of the direct heating are the following reduction of energy consumption, better yield and gain in the reaction duration. From a practical viewpoint, the shorter reaction time enables a faster optimization of the synthesis parameters. 

The microwave chemistry can be applied to practically all inorganic families that do exist (see Introduction). Based on the literature, some interesting facts have been reported and can be summarized as follows stabilization of metastable and novel phases, increase of the phase purity and phase selectivity, short crystallization times and narrow particle-size distribution. 

The explanations for these advantages are still poorly understood but several reasons are usually pointed out very rapid heating rate, uniform heating, unusual interactions between species in the reaction mixture, occurrence of hot spots and enhancement of the dissolution of the reacting species. The occurrence of specific microwave effects is stUl under debate to explain the whole advantages displayed by this technique. For instance, an hypothesis based on enhanced diffusion mechanisms has been recently proposed. Some breakthroughs should be expected to occur with the development of in situ techniques.  

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Microwave synthesis of molecular sieves is a very useful alternative approach, in which case the synthesis proceeds in microwave-transparent glass or plastic reaction vessel. The benefits of nanoporous synthesis under microwave conditions have been reported [12,13]. The most apparent advantage of microwave synthesis is a substantial shortening of the synthesis time. In addition, the special conditions of microwave synthesis can lead also to higher product selectivity [14]. 

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