Catalytic Behavior of Hydrogen Bonded Water in Oligomerization of Silicates

Abstract

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.

Does Water Enable Porosity in Aluminosilicate Zeolites? Porous Frameworks versus Dense Minerals

“…Today, water content is acknowledged as a critical synthesis variable in zeolite synthesis. It has been shown to impact both gelation and crystallization kinetics, − and to influence the final aluminum content as well as the framework topology . With increasing water content, phase transitions from Na-SOD to Na-LTA, , K-EDI to K-CHA, and Na-MOR to Na-MFI, have been reported, with certain topologies requiring more dilute synthesis systems.…”

Structural, electronic, optical, elastic, thermodynamic and thermal transport properties of Cs2AgInCl6 and Cs2AgSbCl6 double perovskite semiconductors using a first-principles study

“…In connection with CASC, it is observed that the bond lengths between Ag and Cl atoms and Sb and Cl atoms were determined to be 2.755 Å and 2.624 Å, respectively. The lengths of the apical bonds ( d abl ) and the equatorial bonds ( d ebl ) are respectively given by 77 where a and c are the lattice parameters and u are the positional parameters of the Cl atoms.…”

First-Principles Calculations to Investigate Coupling Fe Doping with Oxygen Vacancies in Stannic Oxide and Their Physical Properties

“…The Sn 1– x Fe x O 2 octahedron was distorted, with the apical Sn or Fe–O bond length marginally longer than the equatorial Sn or Fe–O bond length. The lengths of the apical bonds ( d abl ) and the equatorial bonds ( d ebl ) are, respectively, given by d normala normalb normall = a u 2 d normale normalb normall = 0.5 a .25em false[ 2 false( 2 u − 1 false) 2 + false( c / a false) 2 false] 1 / 2 where a and c are the lattice parameters and u is the positional parameter of the O atoms. The Sn or Fe atoms possess Wyckoff sites (0, 0, 0), (1/2, 1/2,1/2).…”

“…The Sn 1−x Fe x O 2 octahedron was distorted, with the apical Sn or Fe−O bond length marginally longer than the equatorial Sn or Fe−O bond length. The lengths of the apical bonds (d abl ) and the equatorial bonds (d ebl ) are, respectively, given by80…”