Silica dimerization in the presence of divalent cations

Prasad, D. H. L.; Mitra, Nilanjan

doi:10.1039/d2cp01702d

Cited by 7 publications

(20 citation statements)

References 44 publications

(68 reference statements)

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“…Among the anionic mechanisms, there are also differences in the reaction pathway associated with the arrangement of hydroxyl groups bonded with Si which are categorized as Anionic-I and Anionic-II. 1 Apart from the authors' investigation, the observational difference between neutral and anionic mechanisms has been demonstrated for silica oligomerization reaction by previous investigators. 2,3 Previous studies focused on the anionic pathway "Anionic Condensation → Si−OH rupture" and indicated the catalytic action of water in silica oligomerization.…”

Section: ■ Introductionmentioning

confidence: 75%

“…Anionic condensation can be further categorized into anionic-I and anionic-II depending on the orientation of hydroxyl groups bonded with Si. 1 The complex pathway of anionic-I and anionic-II investigated in this paper has been shown in Figure 1a. The condensation process has been discussed extensively in our previous paper, 1 yet a brief outline of the step with a focus on hydrogen bonding has been presented in the following subsections for completeness of the process.…”

Section: ■ Simulation Methodologymentioning

confidence: 89%

“…Silicate condensation takes place through two different mechanisms: neutral and anionic. − The neutral mechanism consists of a single step of condensation, but the anionic mechanism proceeds through a complex pathway initiating with anionic condensation and terminating with Si–OH rupture. Anionic condensation can be further categorized into anionic-I and anionic-II depending on the orientation of hydroxyl groups bonded with Si . The complex pathway of anionic-I and anionic-II investigated in this paper has been shown in Figure a.…”

Section: Resultsmentioning

confidence: 99%

“…The anionic mechanism involves a deprotonated ion and neutral moiety as reactants, while the neutral mechanism involves only neutral moieties as reactants (Figure b). Among the anionic mechanisms, there are also differences in the reaction pathway associated with the arrangement of hydroxyl groups bonded with Si which are categorized as Anionic-I and Anionic-II . Apart from the authors’ investigation, the observational difference between neutral and anionic mechanisms has been demonstrated for silica oligomerization reaction by previous investigators. , Previous studies focused on the anionic pathway “Anionic Condensation → Si–OH rupture” and indicated the catalytic action of water in silica oligomerization. , Here a complex generalized pathway of silicate oligomerization (shown in Figure a) has been investigated.…”

Section: Introductionmentioning

confidence: 87%

“…Oligomerization of silicates is an important chemical reaction step in sol–gel chemistry, zeolite synthesis, and cement hydration chemistry. It has been demonstrated in previous literature by the authors that there are three different pathways of oligomerization of monocalcium silicates: Neutral, Anionic-I, and Anionic-II. The anionic mechanism involves a deprotonated ion and neutral moiety as reactants, while the neutral mechanism involves only neutral moieties as reactants (Figure b).…”

Section: Introductionmentioning

confidence: 96%

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Catalytic Behavior of Hydrogen Bonded Water in Oligomerization of Silicates

Prasad

Mitra

2023

Inorg. Chem.

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Even though much research has been done to demonstrate the oligomerization of zeolites and silicates, there has been almost no study that investigates the role of hydrogen bonds in these reaction pathways. This study demonstrates the catalytic activity of hydrogen bonds in the silicate oligomerization reaction pathway. The presence of hydrogen bonding has been shown to enhance the energetic favorability of the anionic-I mechanism. Catalysis is prevalent in the Si–OH rupture process of the reaction pathway. Simultaneously, the dependence of the activation barrier on the equatorial or apical nature of the cleaving hydroxyl group has also been shown. The preceding steps such as condensation and fluxional influence the strength of hydrogen bonds. An increase in hydrogen bond strength enhances its catalytic effect, leading to a higher extent of reduction in the activation barrier of the particular reaction step. Even though the quantum study focuses on the oligomerization of calcium silicate as a test case, it can be anticipated that such similar effects can be perceived in general for the oligomerization of silicates containing metallic ions in sol–gel chemistry and zeolite synthesis.

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Section: ■ Introductionmentioning

confidence: 75%

Section: ■ Simulation Methodologymentioning

confidence: 89%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 87%

Section: Introductionmentioning

confidence: 96%

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Catalytic Behavior of Hydrogen Bonded Water in Oligomerization of Silicates

Prasad

Mitra

2023

Inorg. Chem.

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Full‐scale modeling of chemical experiments

Wang,

2023

Smart Molecules

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Computational chemistry methods are playing an increasingly pivotal role in chemical experiments. From quantum chemistry simulations to finite element simulations, researchers can always find an appropriate simulation method to elucidate the specific mechanisms at a certain resolution scale. However, in organic or inorganic synthesis, the synthesis mechanisms span multiple spatial and temporal scales of chemical experiments. Furthermore, the intricate nature of these mechanisms renders it impossible for any single simulation method to provide a comprehensive depiction of the entire process. In this perspective, using zeolite and polymer synthesis simulations as examples, we stress the significance of full‐scale modeling techniques for chemical experiments and urge the corresponding sophisticated simulation platform.

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Simple Molecular Model for Hydrated Silicate Ionic Liquids, a Realistic Zeolite Precursor

Vekeman,

Vandenabeele,

Doppelhammer

et al. 2024

Chem. Mater.

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Despite the widespread use of zeolites in the chemical industry, their formation process is not fully understood due to the complex and heterogeneous structure of traditional synthesis media. Hydrated silicate ionic liquids (HSILs) have been proposed as an alternative. They are truly homogeneous and transparent mixtures with a low viscosity, facilitating experimental characterization. Interestingly, their homogeneous nature and simple speciation bring realistic molecular models of a zeolite growth liquid within reach for the first time. In this work, a simple molecular model is developed that gives insight into the crucial role of the alkali cations (sodium, potassium, rubidium, and cesium). Thereby, molecular dynamics simulations are combined with experimental measurements to demonstrate that the HSIL liquid structure strongly depends on the charge density and concentration of the alkali cation. As the water content increases, it transitions from a glassy network with fast ion exchange to an aqueous solution containing long-lasting solvated ion pairs. Furthermore, simulations reveal that the cation is capable of bringing several silicate monomers together in a glassy network, displaying perfect orientations for condensation reactions that underlie zeolite formation. This work is an important step toward the development of molecular models that can fully describe the early nucleation process of zeolites in combination with experiments.

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Silica dimerization in the presence of divalent cations

Abstract: The presence of divalent cations raises activation energy barrier and delays overall dimerization reaction.

Cited by 7 publications

References 44 publications

Catalytic Behavior of Hydrogen Bonded Water in Oligomerization of Silicates

Catalytic Behavior of Hydrogen Bonded Water in Oligomerization of Silicates

Full‐scale modeling of chemical experiments

Simple Molecular Model for Hydrated Silicate Ionic Liquids, a Realistic Zeolite Precursor

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