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The effect of room temperature aging on the crystallization rate and size of MFI-type crystals synthesized under high temperature was investigated. First, synthesis mixtures yielding MFI-type zeolite were aged at room temperature for periods of time between 1 and 60 days. This was followed by a rapid synthesis in a pre-heated at 230 °C conventional oven. The utilization of a pre-aged initial systems and high heating rates allowed very rapid synthesis of zeolite. The effect of aging time, crystallization temperature, duration of synthesis and aluminum content on the crystal size and yield was systematically studied. Zeolite nanoparticles with sizes ranging from 130 to 260 nm and relatively narrow particle size distributions were synthesized employing the pure-silica system. The obtained nanocrystals were characterized by X-ray diffraction, scanning electron microscopy, dynamic light scattering and N2 adsorption measurements. [Copyright &y& Elsevier]

This feature article highlights recent developments in nanosized zeolites and addresses the question: what will be next? Until recently the limiting step to practical applications was determined by the challenging synthesis of nanosized zeolites in high yield and adequate form. The advances in the synthesis of nanozeolites that provide the basis for future developments and for diverse practical applications are reviewed. The main trends and challenges in processing, characterization and applications of nanosized zeolites are summarized. Particular attention is paid to the processing of nanosized zeolites in terms of their further use. The extending applications of nanosized zeolites in nanotechnology, medicine, pharmaceutical, and food industry, are discussed. [ABSTRACT FROM AUTHOR]

Surfaces of nano-sized ZSM-5 zeolites have been passivated by a chemical liquid deposition (CLD) technique using tetraethylorthosilicate (TEOS). The impact of this post-synthesis treatment has been evaluated in the methanol-to-olefins (MTO) reaction. A two-step surface passivation led to enhanced selectivity towards C 2 –C 4 light olefins, between 10 and 30% in relative, at nearly complete methanol conversion when compared with pristine zeolites. However, these post-treated zeolites exhibited a significant loss in stability. To rationalize these results and establish structure-activity relationships, zeolite catalysts have been thoroughly characterized by nitrogen adsorption–desorption, SEM, XRF, XRD and FTIR techniques. ZSM-5 zeolite (Si/Al = 27) in the form of well-arranged rectangular nanocrystals behave in MTO after silylation as a commercial ZSM-5 zeolite having a Si/Al = 52. [ABSTRACT FROM AUTHOR]