The Role of Interfacial Energy in Zeolite Synthesis

Santen, van Ra Rutger; Keijsper, J.; Ooms, G.; Kortbeek, A.G.T.G.

doi:10.1016/s0167-2991(09)60870-3

Cited by 40 publications

(15 citation statements)

References 26 publications

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“…1,2 Typically, organic molecules employed as structure-directing agents (SDAs) are trapped in zeolite micropore space and have to be eliminated by combustion or chemical treatment in order to open zeolite porosity. Besides playing a template function and thus determining the micropore space, the SDA agents stabilize the zeolite framework 3 and often control zeolite crystal morphology. 4 Extensive use of SDAs in zeolite synthesis resulted in the discovery of many different framework types.…”

Section: ■ Introductionmentioning

confidence: 99%

Control of Na-EMT Zeolite Synthesis by Organic Additives

Georgieva

Vicente

Fernandéz

et al. 2015

Crystal Growth & Design

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Organic additives were used to control the formation of EMT-type zeolite in a sodium-rich initial system. Triethanolamine was employed as a nucleation suppression agent able to complex the aluminum during the synthesis of the EMT-type zeolite. The commonly used tetramethylammonium (TMA) chloride and tetraethylammonium (TEA) chloride as structure directing agents in zeolite synthesis were also employed in this study. The triethanolamine has the most pronounced effect on the crystal growth process of the EMT-type zeolite. The use of triethanolamine resulted in the formation of large crystals (100 nm) with the framework composition different from the counterpart obtained in the organic-free system. Therefore, the function of triethanolamine is attributed to the immobilization of Al in the initial gel and thus partial suppression of zeolite nucleation. The immobilization of a part of Al resulted in the EMT zeolite crystals with a higher Si/Al ratio (1.4). In contrast, the TMA and TEA organic additives have a limited impact on the physicochemical properties of the EMT crystals, the latter being a consequence of large presence of Na in the system. The bulky TMA and TEA ions prevent the aluminosilicate precursor species from agglomeration and formation of dense gels and thus resulting in the crystallization of nanosized EMT zeolite crystals (10−20 nm). ■ INTRODUCTIONZeolites are commonly synthesized from aluminosilicate hydrogels under hydrothermal conditions in the presence of a mineralizing agent (OH − , F − ) and inorganic and/or organic structure-directing agent (SDA), which predetermines to some extent the framework type formed. 1,2 Typically, organic molecules employed as structure-directing agents (SDAs) are trapped in zeolite micropore space and have to be eliminated by combustion or chemical treatment in order to open zeolite porosity. Besides playing a template function and thus determining the micropore space, the SDA agents stabilize the zeolite framework 3 and often control zeolite crystal morphology. 4 Extensive use of SDAs in zeolite synthesis resulted in the discovery of many different framework types. 5 The use of organic SDAs also has certain drawbacks such as (i) high cost of final product, (ii) generation of environmentally undesirable gases due to high temperature combustion of the template, 6 (iii) formation of defects in the zeolite framework during post synthesis treatment, and (iv) even decomposition of zeolite during template elimination. 7 Organic compounds have also been applied in the synthesis of zeolite crystals in order to control the nucleation process and thus to influence the particle size. According to Charnell, 8 the addition of 2,2′,2″-nitrilotriethanol (triethanolamine or TrEA) to zeolite A synthesis gels leads to growth of larger crystals. He proposed that the observed increase in the size of the crystals is due to the "stabilizing and buffering" effect of the TrEA. Recent studies have also confirmed these observations. 9−12 Compared to other organic additives, TrEA can extend the...

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Section: ■ Introductionmentioning

confidence: 99%

Control of Na-EMT Zeolite Synthesis by Organic Additives

Georgieva

Vicente

Fernandéz

et al. 2015

Crystal Growth & Design

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“…The agent responsible for this step is OH -/Si ratio, which at the initial mole ratio of S1 and S2, is not suitable for depolymerizing the silica source enough to produce ZSM-5 zeolite. The double-five-ring (D5R) silicates in ZSM-5 zeolite structure increased with decreasing OH -/Si ratio (Lechert 2000;van Santen et al 1986). Therefore, we need high SiO 2 /Al 2 O 3 mole ratio increasing silica source to synthesis ZSM-5 zeolite.…”

Section: Resultsmentioning

confidence: 99%

Synthesis of nanosized ZSM-5 zeolite using extracted silica from rice husk without adding any alumina source

2014

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The synthesis of analcime and nanosized ZSM-5 zeolites was carried out by a hydrothermal method with silica extracted from rice husk, available as an inexpensive local biowaste, and without the use of an extra alumina source. Amorphous silica (with 88 wt% of SiO 2 ) was extracted from rice husk ash by a suitable alkali solution. The effects of crystallization temperature, time and SiO 2 / Al 2 O 3 ratio of the initial system on the properties of final products were investigated. For the characterization of the synthesized product, X-ray diffraction, scanning electron microscope, energy dispersive X-ray techniques, Fourier transform infrared and Brunauer-Emmett-Teller method were applied. Crystallinity percentages of analcime and nanosized ZSM-5 were 95.86 and 89.56, respectively, with specific surface area of 353.5 m 2 g -1 for ZSM-5. The experimental results revealed that the synthesis of analcime and nanosized ZSM-5 zeolites was more practical with using silica extracted from inexpensive raw materials, while the whole crystallization process was accomplished without adding any alumina source during.

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“…in silicalite [9] corresponding to ca. 8 missing tetrahedral sites [10]. This means that macrocavities could be formed in these zeolites, where the TPA cations are less strongly held than in the zeolitic channels and hence, their thermal decomposition is easier.…”

Section: Resultsmentioning

confidence: 99%

Thermal behaviour of the tpa IONS in ZSM-5 zeolite: II. Effect of crystal size and grinding of silicalite-1

Crea

Giordano

Mostowicz

et al. 1990

Journal of Thermal Analysis

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RENDE, 87030 RENDE (CS), ITALYThermal decomposition of Silicalite-1 crystals of various size was studied. The crystals were in as-made form and upon grinding. The DTA and DTG curves show differences in the temperature of thermal decomposition of TPA species occluded in the as-made crystals. These differences disappear upon grinding. The explanation of this phenomena is given.Silicalite-1, the Al-free analogue of ZSM-5 zeolite was first prepared by E. M. Flanigen et al. [1]. It has the same crystal structure as the ZSM-5 zeolite which has been applied as a catalyst in MTG and other petrochemical processes [2].Synthesis of the ZSM-5 zeolite and its aluminium deficient end-member silicalite has been the topic of a large number of investigations [3]. The parameters affecting the growth of large silicalite crystals and the effect of reactant concentration on crystal morphology have been reported by Hayhurst et aL [4,5].The organic compounds used as either structure-directing and/or space filling species in a high-silica zeolite synthesis are generally occluded in the zeolite channels and cavities either in an intact or in a modified state [3,6]. The state of tetrapropylammonium (TPA) ions, occluded in ZSM-5 channels has been most thoroughly investigated by thermal analysis combined with mass spectrometry [7] or 13C-NMR spectroscopy [8]. TPA ions decompose by the Hoffman reaction to give an olefin and trialkylamine [7].The three DTA peaks (B, C1 and C2) have been assigned [8] to decomposition of different TPA species occluded into the zeolitic channels. In the case of Al-free silicalite, the low temperature (ca 380 ~ peak B is attributed [9] to less strongly held or "outer shell" strained TPA ions. A peak C1 (ca. 425 ~ is assigned to inner ions neutralizing SiO-negative charges of John Wiley & Sons, Limited, Chichester Akadgrm'ai Kiad6, Budapest

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The Role of Interfacial Energy in Zeolite Synthesis

Cited by 40 publications

References 26 publications

Control of Na-EMT Zeolite Synthesis by Organic Additives

Control of Na-EMT Zeolite Synthesis by Organic Additives

Synthesis of nanosized ZSM-5 zeolite using extracted silica from rice husk without adding any alumina source

Thermal behaviour of the tpa IONS in ZSM-5 zeolite: II. Effect of crystal size and grinding of silicalite-1

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