Supercritical Water Properties and Beckmann Rearrangement Reaction: First Principles Molecular Dynamics Study

Abstract

Physical and chemical properties of supercritical water were investigated by first principles molecular dynamics (FPMD). Hydrogen bonds are present in supercritical water, but do not form a network, resulting in formation of various sizes of clusters. FPMD confirmed that Beckmann rearrangement reaction of cyclohexanone oxime to ε-caprolactam occurs via a hydronium ion in the supercritical water at 670 K and 0.7 g/cm3, not due to the high temperature but to the low density. The hydronium ion is not completely solvated by three water molecules because of the low density of the supercritical water, resulting in high reactivity. No Beckmann rearrangement reaction takes place even at 670 K and normal water density of 1 g/cm3, since the hydronium ion is stabilized by complete solvation.