Microwave Techniques in the Synthesis and Modification of Zeolite Catalysts. A Review

Abstract

Microwave dielectric heating is a convenient and effective way of bringing about chemical reactions in suitable (usually polar) media. Microwave-mediated organic synthesis has been the subject of considerable research and microwave heating is being increasingly applied to the synthesis and modification of zeolites and related microporous and mesoporous catalysts. The observed rate enhancements are caused by a variety of thermal effects, including very high rates of temperature rise, bulk superheating and (in non-homogeneous systems) differential heating. Specific, non-thermal activation is unlikely and can usually be excluded. The microwave synthesis of zeolites, zeotypes and mesoporous materials is reviewed, with emphasis on those aspects which differ from conventional thermal methods. Such standard methods are not displaced by microwave techniques and may in some instances be preferable. However, microwave synthesis does offer a high probability of rapid (and in some cases selective) reaction to give a pure product of good crystal quality. Non-synthetic applications of microwave heating in zeolite catalysis are also briefly described. A review with 118 references.