Zeolite beta mechanisms of nucleation and growth

Hould, Nathan D.; Foster, Andrew J.; Lobo, Raúl F.

doi:10.1016/j.micromeso.2010.11.024

Cited by 55 publications

(62 citation statements)

References 63 publications

(91 reference statements)

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“…SAXS provides valuable information on the sizes and shapes of the evolving nanoscopic particles. It has been used frequently to monitor the formation and growth of silicate nano objects in the early stages of crystallization …”

Section: Resultsmentioning

confidence: 99%

“…The aim of the present contribution is to study the early stages of the formation of zeolite beta from clear sols using TEAOH as the SDA in the presence or absence of NAs in the reaction mixture by controlling the initial Si/OH ratio. Although the mechanism of zeolite beta crystallization has been the subject of several studies in the past, the current contribution uses a combination of methods to register species in precursor solutions/sols. In addition, the evolution of these objects during crystallization under hydrothermal conditions is monitored.…”

Section: Introductionmentioning

confidence: 99%

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Zeolite Beta Formation from Clear Sols: Silicate Speciation, Particle Formation and Crystallization Monitored by Complementary Analysis Methods

Castro

Haouas

Lim

et al. 2016

Chemistry A European J

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The formation of silicate nanoaggregates (NAs) at the very early stages of precursor sols and zeolite beta crystallization from silicate nanoparticles (NPs) are investigated in detail using a combination of different analysis methods, including liquid-state Si, Al, N, and H NMR spectroscopy, mass spectrometry (MS), small-angle X-ray scattering (SAXS), X-ray diffraction (XRD), and transmission electron microscopy at cryogenic temperatures (cryo-TEM). Prior to hydrothermal treatment, silicate NAs are observed if the Si/OH ratio in the reaction mixture is greater than 1. Condensation of oligomers within the NAs then generates NPs. Aluminum doped into the synthesis mixtures is located exclusively in the NPs, and is found exclusively in a state that is fourfold connected to silicate, favoring their condensation and aggregation. These results are in agreement with general trends observed for other systems. Silicate NAs are essential intermediates for zeolite formation and are generated by the aggregation of hydrated oligomers, aluminate, and templating cations. Subsequent further intra-nanoaggregate silicate condensation results in the formation of NPs. H and N liquid NMR as well as diffusion ordered spectroscopy (DOSY) experiments provide evidence for weakly restricted rotational and translational mobility of the organic template within NAs as a consequence of specific silicate-template interactions. NAs thus appear as key species in clear sols, and their presence in the precursor sol favors silicate condensation and further crystallization, promoted either by increasing the Si/OH ratio or by heating.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Zeolite Beta Formation from Clear Sols: Silicate Speciation, Particle Formation and Crystallization Monitored by Complementary Analysis Methods

Castro

Haouas

Lim

et al. 2016

Chemistry A European J

View full text Add to dashboard Cite

show abstract

“…X-ray (SAXS, WAXS) and neutron scattering (SANS) techniques are also applied for in situ studies of zeolite formation [32,[36][37][38][39][40]. The analysis is not limited to clear solution samples, but gel-like samples used in typical synthesis can also be measured.…”

Section: Methods For Analyzing and Understanding Silicates In Solutiomentioning

confidence: 99%

The formation of zeolites from solution – Analysis by mass spectrometry

Lim

Schräder

2013

Microporous and Mesoporous Materials

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“…To overcome these problems, many efforts have been made to prepare large pore substances with zeolite specifications. A considerable number of researches have been reported on zeolite synthesis and development [22]. For example, Ryoo et al prepared C 38 H 82 N 2 Br 2 as SDA for initial load and by using this SDA, the scientists prepared mesosheet zeolite of only 2.5 nm width.…”

Section: Introductionmentioning

confidence: 99%

Fine-Tuning Synthesis and Characterization of Mono-Sized H-Beta Zeolite-Supported Palladium-Iridium Nanoparticles and Application in the Selective Hydrogenation of Acetylene

2017

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Abstract:In this research, a mono-sized Beta zeolite support synthesized by the solvothermal method was used in the selective acetylene to ethylene hydrogenation reaction with minimum coke build up on the catalyst surface. Tetrapropylammonium hydroxide (TPAOH), tetrapropylammonium bromide (TPABr), n-butylamine, and morpholine were used as structure direct agents (SDA) in the support to obtain various shapes. The characterization results show that although the Si/(Al + SDA) ratio has no effect on the phase purity of support, it has a remarkable effect on porosity, crystal size, shape, and structure of micropores. After comparing characterization results, the developed support, based on TPAOH, was selected and modified by different metals (Ce, Ir, Ag, and Pd) using the incipient wetness co-impregnation method. Since there is an interaction between selectivity and conversion, the optimum metal content in the synthesized catalysts and reaction condition were determined to achieve the desired acetylene conversion and ethylene selectivity. The physicochemical transformation of the developed optimum catalysts was determined using different techniques. Based on the characterization and cata-test results, the catalyst which contains 0.29% Ir and 0.08% Pd presents a better performance and higher stability compared to the other catalysts due to the moderate size and mono layer dispersion of the metals on the support. The experimental results show that acetylene conversion and ethylene selectivity approach 97% and 92% at 55 • C, respectively.

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Zeolite beta mechanisms of nucleation and growth

Cited by 55 publications

References 63 publications

Zeolite Beta Formation from Clear Sols: Silicate Speciation, Particle Formation and Crystallization Monitored by Complementary Analysis Methods

Zeolite Beta Formation from Clear Sols: Silicate Speciation, Particle Formation and Crystallization Monitored by Complementary Analysis Methods

The formation of zeolites from solution – Analysis by mass spectrometry

Fine-Tuning Synthesis and Characterization of Mono-Sized H-Beta Zeolite-Supported Palladium-Iridium Nanoparticles and Application in the Selective Hydrogenation of Acetylene

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