Crystallization phenomena in seeded zeolite syntheses

A facile method for the size‐controllable synthesis of titanium silicalite‐1 (TS‐1) is presented. A tetrapropylammonium bromide hydrothermal system was used, and the amount of seeds (silicalite‐1 suspension) and crystallization time were tuned to control the crystal size. The crystal size could be adjusted from 200 to 1200 nm by varying the seed amount from 12 to 0.05 wt %. Crystallization time plays a less important role than the seed amount on the crystal size. TS‐1 samples with different crystal sizes were characterized and evaluated in propene epoxidation. The catalytic activity and selectivity of propene oxide are enhanced by decreasing the crystal size from 1200 to 200 nm because the diffusion limitation is eliminated gradually. The seed is significant for this system, as a lack of seeds leads to poor crystallization and low catalytic activity. The mechanism of the seed function was studied by simulating the transformation process of the seed in the TS‐1 synthesis system.

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“…Researchers have expressed different opinions on the function of seeds in crystallization 48–50. The seed may perform as a nucleus directly 51.…”

Section: Resultsmentioning

confidence: 99%

Enhanced Catalytic Performance of Titanium Silicalite‐1 in Tuning the Crystal Size in the Range 1200–200 nm in a Tetrapropylammonium Bromide System

et al. 2015

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“…It was found that MTW-type zeolite could be obtained from the seeded, OSDA-free gel having a wide range of chemical compositions, whereas ZSM-5 (MFI-type zeolite) and mordenite (MOR-type zeolite) were crystallized from the same gels in the absence of ZSM-12 seeds after a long heating period [17]. Such aberrant crystallization behavior is not common in general seed-assisted syntheses of zeolites because in these cases, the seeds are used only to promote the crystallization rate of target zeolites having the same structure as that of the seeds [28][29][30][31][32][33].…”

Section: Introductionmentioning

confidence: 93%

OSDA-free synthesis of MTW-type zeolite from sodium aluminosilicate gels with zeolite beta seeds

Kamimura

Iyoki

Elangovan

et al. 2012

Microporous and Mesoporous Materials

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“…In general, zeolite crystallization is focused on because of its notable influence on the performances of the synthetic zeolite products. Various materials including crystal seeds (Edelman et al 1989), aged mother liquor (Gora and Thompson 1997), inorganic compounds ) as well as organic compounds (Charnell 1971;Basaldella and Tara 1998;Kim et al 2009) were used for governing the crystallization process or varying the crystal sizes of zeolite products. Controlled addition of organic additive to zeolite synthesis systems was most extensively investigated (Barrer 1981).…”

Section: Introductionmentioning

confidence: 99%

Effects of organic additives on crystallization process and the adsorption performances of zeolite A

Sun

Shen

2012

Adsorption

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The crystallization of zeolite A was monitored by measuring the adsorption capacities of synthetic products. The influences of organic additives on the crystallization process and adsorption performances of zeolite were investigated. SDS (sodium dodecyl sulphonate), TWEEN (Tween-80), and PEG (poly(ethylene glycol)) shorten the induction period by reducing the interfacial energy while SCMC (sodium carboxymethylcellulose) can prolong the induction period by increasing the interfacial energy. TEA (triethanolamine) can also suppress the nucleation through reducing the effective supply of aluminum. All the organic additives but SCMC diminish the rate of crystal growth. CTAB (cetyltrimethylammonium bromide) causes the destruction of crystal structure and reduce the concentration of OH − ions. As a result, the rate of crystal growth is significantly reduced. Meanwhile, PAM (poly(acrylamide)), SDS, TWEEN, HMTA (hexamethylenetetramine), and PEG increase the viscosities of synthesis systems, thus, diminish the growth rate. PAM restrains the transformation of zeolite A crystal into hydroxysodalite one, therefore, tremendously improves the stability of crystals of zeolite A. In addition, PAM can promote the rates of n-hexane adsorption on zeolite 5A because of the impact of PAM on the crystal-size distributions of zeolite 5A.

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Crystallization phenomena in seeded zeolite syntheses

Cited by 52 publications

References 10 publications

Enhanced Catalytic Performance of Titanium Silicalite‐1 in Tuning the Crystal Size in the Range 1200–200 nm in a Tetrapropylammonium Bromide System

Enhanced Catalytic Performance of Titanium Silicalite‐1 in Tuning the Crystal Size in the Range 1200–200 nm in a Tetrapropylammonium Bromide System

OSDA-free synthesis of MTW-type zeolite from sodium aluminosilicate gels with zeolite beta seeds

Effects of organic additives on crystallization process and the adsorption performances of zeolite A

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