Possible recovery of crown ethers occluded in FAU- and EMT-type zeolites

Dougnier, F.; Guth, J.L.

doi:10.1016/0927-6513(95)00082-8

Cited by 5 publications

(2 citation statements)

References 18 publications

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“…However, the use of other structure-directing agents and various initial systems have resulted in intergrown EMT-FAU (CSZ-1, ECR-30, ZSM-20, ZSM-3) materials. − Thus, until recently, the synthesis of pure EMT-type zeolite was possible solely by employing an exotic template (18-crown-6 ether) . Many attempts have been carried out to reduce the consumption of crown ether, for instance, by recycling organic structure-directing agents (OSDAs) after the synthesis or using the “SINTEF” tumbling approach, surfactants, and less-expensive organic and inorganic auxiliary additives. − Although the synthesis of the EMT-type zeolite was optimized, still the use of 18-crown-6 ether remained indispensable for the production of this promising material.…”

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confidence: 99%

Nucleation and Crystal Growth Features of EMT-Type Zeolite Synthesized from an Organic-Template-Free System

Goupil

Vicente

et al. 2012

Chem. Mater.

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The process of formation of ultrasmall EMT-type zeolite from organic-template-free homogeneous suspensions is presented. The formation of transparent uniform suspension utilizing sodium aluminate, sodium silicate, and sodium hydroxide under controlled mixing is found to be of primary importance to control the nucleation and growth process of EMT-type crystals. The investigation of zeolite intermediates reveals the formation of uniformly sized gel particles (5−10 nm in size). The mean hydrodynamic diameter of the crystalline EMT-type zeolite corresponds to the size of the amorphous particles formed after preparation of the clear precursor suspension. Controlled formation of uniform precursor particles predetermines, to great extent, the following nucleation and growth steps and, thus, the characteristics of the ultimate product. The amorphous particles are transformed to single EMT-type crystals 6−15 nm in size at 303 K within 36 h. Small changes in the initial composition or the preparation procedure lead to the formation of other sodalite-cage-containing zeolites. Thus, it is of critical importance to control the nucleation kinetics in order to obtain the EMT-type material as pure phase. Besides the EMT zeolite, the crystallization fields of other zeolites upon low-temperature synthesis conditions are studied. The careful control of gel chemistry, combined with slow nucleation kinetics at low temperature, can provide access to important nanoscale zeolites while avoiding the use of expensive organic templates.

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Section: Introductionmentioning

confidence: 99%

Nucleation and Crystal Growth Features of EMT-Type Zeolite Synthesized from an Organic-Template-Free System

Goupil

Vicente

et al. 2012

Chem. Mater.

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“…The synthesis of pure EMT-type zeolite is possible by templating with the expensive 18-crown-6 ether and using tightly controlled synthesis parameters (7). Many studies have been carried out to reduce the consumption of the crown ether template, for instance, by recycling after the synthesis (15) or using the socalled "SINTEF" tumbling approach (16,17), steam-assisted crystallization (18), surfactants (19), or other organic and inorganic auxiliary additives (20)(21)(22). Although the cost of producing EMT has been reduced, all attempts toward a synthesis of EMT-type zeolite without an organic structure-directing agent (OSDA) have been un-successful thus far.…”

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confidence: 99%

Capturing Ultrasmall EMT Zeolite from Template-Free Systems

Chateigner

Bein

et al. 2012

Science

267

202

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Small differences between the lattice energies of different zeolites suggest that kinetic factors are of major importance in controlling zeolite nucleation. Thus, it is critical to control the nucleation kinetics in order to obtain a desired microporous material. Here, we demonstrate how careful investigation of the very early stages of zeolite crystallization in colloidal systems can provide access to important nanoscale zeolite phases while avoiding the use of expensive organic templates. We report the effective synthesis of ultrasmall (6- to 15-nanometer) crystals of the large-pore zeolite EMT from template-free colloidal precursors at low temperature (30°C) and very high yield.

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