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.