Hierarchical zeolites: Synthesis and catalytic properties

Synthesis, characterization and application of hierarchical zeolites are becoming a subject of increasing interest among scientists. Hierarchical zeolites possessing secondary porosity at meso- and macroscale, imposed on primary microporous structures are an original class of porous materials exhibiting both molecular sieving ability and fast mass transport. These materials, due to the combination of catalytic properties of conventional zeolites with enhanced access and transport of reagents in additional meso- or microporosity, constitute an effective solution to the problem of mass transport, which occurs while using conventional zeolites in catalytic reactions. The latter allows molecules of substrates to access the active sites that are located within micropores and reduce the catalysts, leading to increase reaction rates and catalyst life-time (slower deactivation removal time of product molecules). Besides, secondary porosity of hierarchical zeolites creates an ideal space for deposition of active catalytic phases controlling their size and allows attaining high dispersion and strong interaction between zeolite and the medium. This work focuses on the review of synthesis methods of hierarchical zeolites and their application in selected catalytic reactions. (C) 2017 Elsevier Inc. All rights reserved.