Abstract
A novel template-free colloidal assembly method that combines colloidal zeolite (silicalite-1) suspensions in a water-in-oil emulsion with an evaporation-induced assembly process has been developed for preparing hierarchical micro-/mesoporous zeolite microspheres (MZMs). Such particles have an interconnected mesoporosity and large mesopore diameters (25–40 nm) combined with 5.5 Å diameter micropores of the zeolite nanoparticles. The method developed has the advantages of employing mild synthesis conditions, a short preparation time, and not requiring the use of a mesoporogen template or post-treatment methods. The method provides a new range of micro-/mesoporous zeolites with tunable mesoporosity dictated by the size of the zeolite nanoparticles. It also offers the possibility of combining several zeolite particle sizes or optionally adding amorphous silica nanoparticles to tune the mesopore size distribution further. It should be generally applicable to other types of colloidal zeolite suspensions (e.g. ZSM-5, zeolite A, beta) and represents a new route amenable for cost-effective scale-up.
Highlights
Zeolites have been extensively studied and used for decades as catalysts, sorbents and ion exchange materials.[1]
We present a simple and efficient evaporationdriven template-free colloidal assembly procedure for the preparation of hierarchical micro-/mesoporous zeolite microspheres (MZMs)
The synthesis process is illustrated in Scheme 1 and based on the use of previously prepared discrete zeolite nanoparticles as building blocks
Summary
Zeolites have been extensively studied and used for decades as catalysts, sorbents and ion exchange materials.[1]. Steam-Assisted Crystallization (SAC) has been used to prepare mesopore zeolite beta and MFI-type zeolites, obtaining mesopore size distributions up to 60 nm and pore volumes up to 0.9 ml gÀ1.33–35 Another method is the nanofusion, at which nanozeolites are fused into hierarchical zeolite aggregates under drying and calcination steps.[36] Mesoporous zeolite beta was prepared by nanofusion of zeolite crystals of 20–40 nm, forming mesopores up to 29 nm in size with surface areas between 656 and 766 m2 gÀ1 Some of these methods still have some drawbacks: high crystallization temperatures, long preparation times, low control of the mesopore size and non-de ned morphology of the particles. The total pore volume was estimated at p/p0 of 0.99
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