Mechanism of the Initial Stage of Silicate Oligomerization

Zhang, Xueqing; Trinh, Thuat T.; Santen, Rutger A. van; Jansen, Apj Tonek

doi:10.1021/ja110357k

Cited by 106 publications

(233 citation statements)

References 47 publications

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“…[57][58][59][60] Fig. It is computationally not feasible to study a realistic reaction mixture with QM methods, but kinetic models have been developed that use output of QM calculations to determine the reaction profiles of the relevant reactions and then describe the reacting mixture with thousands of monomers using Monte Carlo methods.…”

Section: Review Articlementioning

confidence: 99%

See 1 more Smart Citation

Advances in theory and their application within the field of zeolite chemistry

et al. 2015

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Zeolites are versatile and fascinating materials which are vital for a wide range of industries, due to their unique structural and chemical properties, which are the basis of applications in gas separation, ion exchange and catalysis. Given their economic impact, there is a powerful incentive for smart design of new materials with enhanced functionalities to obtain the best material for a given application. Over the last decades, theoretical modeling has matured to a level that model guided design has become within reach. Major hurdles have been overcome to reach this point and almost all contemporary methods in computational materials chemistry are actively used in the field of modeling zeolite chemistry and applications. Integration of complementary modeling approaches is necessary to obtain reliable predictions and rationalizations from theory. A close synergy between experimentalists and theoreticians has led to a deep understanding of the complexity of the system at hand, but also allowed the identification of shortcomings in current theoretical approaches. Inspired by the importance of zeolite characterization which can now be performed at the single atom and single molecule level from experiment, computational spectroscopy has grown in importance in the last decade. In this review most of the currently available modeling tools are introduced and illustrated on the most challenging problems in zeolite science. Directions for future model developments will be given.

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Section: Review Articlementioning

confidence: 99%

“…59 Another study discusses the structure-directing role of counterions for the oligomerization reactions. Near-neutral solutions favor the formation of linear species, while in more basic conditions, ring closure is favored.…”

Section: Review Articlementioning

confidence: 99%

Advances in theory and their application within the field of zeolite chemistry

et al. 2015

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“…These small units, called pre-nucleation clusters 49 , have been thoroughly studied in the case of silica-rich solutions, both experimentally [11][12][13][14][15][16][17][18] and theoretically 19,21,[50][51][52] . It has been shown that their average concentration depends on several factors such as temperature, initial silica concentration, pH and the presence of additional cations.…”

Section: B Formation Of Oligomers In the Aqueous Solutionmentioning

confidence: 99%

“…The whole precipitation process is usually described as a succession of steps. First, silica monomers bind to each others to form small oligomers (dimers, trimers, tetramers, etc) in the aqueous solution, before, eventually, condensed spherical nanoparticles precipitate [11][12][13][14][15][16][17][18][19][20][21] . The first stage of monomer association is promoted by increasing the total aqueous (SiO 2 ) aq concentration and by decreasing temperature.…”

Section: Introductionmentioning

confidence: 99%

Precipitation mechanism of amorphous silica nanoparticles: A simulation approach

Noguera

Fritz

Clément

2015

Journal of Colloid and Interface Science

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Hypothesis: Despite its importance in numerous industrial and natural processes, many unsolved questions remain regarding the mechanism of silica precipitation in aqueous solutions: order of the reaction, role of silica oligomers, existence of an induction time and characteristics of the particle population. This may be traced back, in past models, to the lack of account of the first stages of nucleation, size dependence of the growth law, and full particle population.Computational method: A microscopic description of the nucleation and growth of amorphous silica nanoparticles is achieved which reproduces a large set of experimental measurements, under various thermodynamic conditions. The time evolution of the solution supersaturation and of the precipitate characteristics is established.Findings : A growth law of order 6 allows reproducing experimental results, without being correlated to the presence of silica oligomers in the aqueous solution. The saturation plateaus are shown not to be due to an induction period. The characteristics of the particle population are more complex than assumed by simple precipitation models (Johnson-Mehl-Avrami-Kolmogorov or Chronomal models) and strongly depend on how supersaturation is reached. Such a microscopic approach thus proves to be well suited to elucidate the mechanism of nanoparticle formation in natural and industrial contexts.

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“…The transformation of molecular precursors to micron-sized zeolite crystals involves several steps [19]. A number of review and original articles are available on the possible mechanisms of silicalite-1 crystallization [16,[20][21][22][23][24]. Three possible mechanisms, as shown in Figure 12.2a [16], are distinguished and the crucial differences lie in two points: the size range in which the first ordered units are formed and the size range in which particles aggregate to form larger structures.…”

Section: Synthesismentioning

confidence: 99%