EMT zeolite synthesis: Na+ vs. OH? effect

Dougnier, F.; Guth, J.L.

doi:10.1039/c39950000951

Cited by 7 publications

(5 citation statements)

References 2 publications

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“…At 296 K, in addition to the gas‐phase line at 0 ppm, the spectrum exhibits a single line at δ =85 ppm that corresponds to adsorbed xenon. This shift is completely consistent with the 129 Xe NMR spectrum that we recorded with a reference EMT‐type sample synthesized with 18‐crown‐6 ether as the templating agent 52. As the temperature was decreased, the chemical shift increased and the signal split into two components that become broader.…”

Section: Resultssupporting

confidence: 87%

“…The 129 Xe signal sensitivity is enhanced by a factor of 10 3 –10 5 . Thus, the HP 129 Xe NMR spectroscopy technique is particularly useful for systems with low surface areas and/or long spin‐lattice relaxation times ( T 1 ), and has found widespread applications, for example, in the characterization of surfaces, nanocrystals or thin films, porous materials, magnetic resonance imaging, and medical imaging, sensors 52. 53, 59–61…”

Section: Methodsmentioning

confidence: 99%

“…This shift is completelyc onsistent with the 129 Xe NMR spectrum that we recorded with areference EMT-type sample synthesized with 18-crown-6 ether as the templating agent. [52] As the temperature was decreased, the chemicals hift increased and the signal split into two components that become broader.S pectra were also recorded with the lasers off at temperaturesb elow 213 K. Under these conditions, one signal is present that corresponds to the high chemical shift line of the HP spectra. This peak is due to purely thermally polarizedX eb elow 193 K, which provest hat the HP Xe www.chemeurj.org nuclei lose their polarization rapidly in the zeolite pores and are not exchanged by HP Xe during the time delay between two subsequent radio frequency pulses.…”

Section: Xe Nmr Studymentioning

confidence: 99%

“…The 129 Xe signal sensitivity is enhancedb y af actor of 10 3 -10 5 .T hus,t he HP 129 Xe NMR spectroscopy technique is particularly useful for systemsw ith low surface areas and/or long spin-lattice relaxation times (T 1 ), and has found widespreada pplications, for example, in the characterization of surfaces, nanocrystals or thin films, porous materials, magnetic resonance imaging, and medical imaging, sensors. [52,53,[59][60][61] TEM and 3D TEM Conventional TEMimaging was performed at the Central Facility for Advanced Microscopy and Microanalysis of the University of California at Riverside by using an FEI CM300 TEM equipped with aL aB 6 cathode and an EDAX Genesis EDSs ystem fitted with a3 0mm 2 Si(Li)d etectorw ith ar esolution of 128 nm at Mn Ka at 200 and 300 kV accelerating voltages.S amples were prepared by putting some of the ungrounds ynthesis powders in distilledwater,dispersing them by using ultrasonic agitation, and depositing ad ropleto ft he resulting suspension onto Cu grids coated with at hin holey carbon support film. Images were recorded by using aG atan MSC794C CD camerai n low-dosemode.…”

Section: Synthesis Of Emt-type Zeolitementioning

confidence: 99%

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3D Study of the Morphology and Dynamics of Zeolite Nucleation

Melinte

Georgieva

Springuel‐Huet

et al. 2015

Chemistry A European J

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The principle aspects and constraints of the dynamics and kinetics of zeolite nucleation in hydrogel systems are analyzed on the basis of a model Na-rich aluminosilicate system. A detailed time-series EMT-type zeolite crystallization study in the model hydrogel system was performed to elucidate the topological and temporal aspects of zeolite nucleation. A comprehensive set of analytical tools and methods was employed to analyze the gel evolution and complement the primary methods of transmission electron microscopy (TEM) and nuclear magnetic resonance (NMR) spectroscopy. TEM tomography reveals that the initial gel particles exhibit a core-shell structure. Zeolite nucleation is topologically limited to this shell structure and the kinetics of nucleation is controlled by the shell integrity. The induction period extends to the moment when the shell is consumed and the bulk solution can react with the core of the gel particles. These new findings, in particular the importance of the gel particle shell in zeolite nucleation, can be used to control the growth process and properties of zeolites formed in hydrogels.

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Section: Resultssupporting

confidence: 87%

Section: Methodsmentioning

confidence: 99%

Section: Xe Nmr Studymentioning

confidence: 99%

Section: Synthesis Of Emt-type Zeolitementioning

confidence: 99%

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3D Study of the Morphology and Dynamics of Zeolite Nucleation

Melinte

Georgieva

Springuel‐Huet

et al. 2015

Chemistry A European J

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“…Therefore, the sodium phosphate must play an auxiliary role in the synthesis of EMT like surfactants . Moreover, for the Na + has little effect on the synthesis of EMT, the active species must be PO 4 3- .…”

mentioning

confidence: 99%

Synthesis of Zeolite EMT with Aid of Sodium Phosphate

et al. 2002

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Since the successful synthesis of pure hexagonal faujasite EMT was reported in 1989 by Delprato and co-workers, 1 there has much interest in this potentially useful large-pore zeolite with 12-ring aperture and twodimensional direct channel systems. [2][3][4][5][6][7][8][9][10][11][12] In the alkylation of isobutane with 2-butene, EMT has been found to perform much better than its cubic analogues FAU. 13,14 However, a major disadvantage of the EMT zeolite was the high cost of the templates1,4,7,10,13,-16-hexaoxacycleoctadecane. Approaches to reduction of the amount of 18-crown-6 ether include the use of surfactants 15 and auxiliary organic additives 16,17 and the SINTEF method reported by Wendelbo et al. 21,22 The amount of 18-crown-6 ether has been reduced to 0.4-0.5 per Al 2 O 3 in recent reports. 15-20 However, it would result in a mixture of EMT and FAU and eventually in pure FAU if the amount of 18-crown-6 ether was reduced further. [15][16][17][18]21 Besides that, with the decrease of the amount of 18-crown-6 ether, the crystallization time also increased greatly. 21 Recently, the EMT was synthesized with an 18-crown-6 ether/Al 2 O 3 ratio of 0.14 via the SINTEF method. 21,22 Unfortunately, the crystallinity of the product was low, even though it had undergone crystallization for a long period of time and other phases would form while prolonging the crystallization time further. Long crystallization time was also a drawback in acquiring a more cost-effective procedure for synthesis of EMT. Approaches toward resolving this problem such as increasing temperature, raising the pH, and adding fluoride 18 have not been particularly successful because those methods would in some case lead to more defects of structure and mixed phases of crystals.On the other hand, as was well-known, the evolution of the hydrogel toward the crystalline was a rather complex physico-chemical process. For the crystallization occurred in an aqueous medium upon heating, the water and cation-water complexes were considered to play an important role during crystallization. 23 In the case of EMT, it was synthesized in a dense gel that was highly thixotropicsthe viscosity of gel without agitation was 10 times that with agitation. 19,21 It would bring about the slow crystallization rate of EMT and increase the probability of nucleating other phases. 21 So improving the transportation of the water-crowded inorganic species and structural-directing agents was of great help in shortening the crystallization time. Here, we provide an approach to successfully synthesize pure zeolite EMT with high efficiency, that is, the synthetic period is shortened from 30 days to 6 days and the ratio of 18-crown-6 ether/Al 2 O 3 decreases to 0.33 by the aid of the auxiliary agent of Na 3 PO 4 ‚12H 2 O.The procedure for synthesizing EMT was based on the Delprato method. The NaOH, auxiliary, and 18-crown-6 ether were dissolved in distilled water first and then colloidal silica (26 wt % SiO 2 , 0.5 wt % Na 2 O) was added to the mixture dropwise with stirring...

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Synthesis of EMT-rich faujasite in the presence of organic template of low-cost polyquaternium-6

Liu

et al. 2007

J Porous Mater

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EMT zeolite synthesis: Na+ vs. OH? effect

Abstract: Addition of sodium chloride to hydrogels containing 18-crown-6 ether shows that EMT zeolite synthesis is controlled by the ratio OH-:A1203 rather than by Na+:AI2O3.

Cited by 7 publications

References 2 publications

3D Study of the Morphology and Dynamics of Zeolite Nucleation

3D Study of the Morphology and Dynamics of Zeolite Nucleation

Synthesis of Zeolite EMT with Aid of Sodium Phosphate

Synthesis of EMT-rich faujasite in the presence of organic template of low-cost polyquaternium-6

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