Synthesis of Zeolite Na-A in The Presence of Triethanolamine

Scott, G.; Dixon, Anthony G.; Sacco, Albert; Thompson, Robert W.

doi:10.1016/s0167-2991(08)61734-6

Cited by 7 publications

(3 citation statements)

References 8 publications

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“…However, the size of these samples is difficult to see clearly in the SEM pictures; therefore a TEM study was performed (see below). This result points out the impact of TrEA on the crystallization process where the immobilization of a part of Al restricts the number of viable nuclei that continue growing . Thus, larger zeolite crystals are obtained.…”

Section: Resultsmentioning

confidence: 72%

“…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. − Compared to other organic additives, TrEA can extend the induction period by formation of chelate complexes with Al in the initial gel. Namely, the TrEA can inhibit the nucleation through reducing the effective distribution of aluminum in the precursor suspension and the degree of supersaturation of the synthesis mixture.…”

Section: Introductionmentioning

confidence: 72%

“…This result points out the impact of TrEA on the crystallization process where the immobilization of a part of Al restricts the number of viable nuclei that continue growing. 11 Thus, larger zeolite crystals are obtained. In addition, more abundant formation of crystalline agglomerates in the 1-EMT sample is observed.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

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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: Resultsmentioning

confidence: 72%