Kinetics for the hydrolysis of Ti(OC<inf>3</inf>H<inf>7</inf>)<inf>4</inf>: A molecular dynamics simulation study

Using molecular dynamics (MD) simulations in conjunction with a reactive force field method, the chemical kinetics of the hydrolysis of titanium tetraisopropoxide (Ti(OC3H7)4, TTIP) at high-temperature conditions is investigated. The MD simulations allow for presenting the complete dynamic process of the TTIP conversion at the atomic level. The rate constant of TTIP hydrolysis at 1 atm is estimated to be k=1.23×1014×exp(-11,323/T(K))mol-1cm3s-1 using a second-order reaction model. On the basis of Ti-containing intermediate species profiles, the evolutions of the main decomposition products during the TTIP hydrolysis are identified and key reaction pathways are elucidated. The results show that the clusters are formed before TiO2 molecules are observed. During the decomposition, Ti-containing species with one or two C-O bonds and carbon-free species with more than two Ti-O bonds are formed and undergo two separate pathways. One is the combination via the formation of Ti-O-Ti bridges, forming early clusters that serve as precursors for large TiO2 nanoparticles. The other is the further decomposition to smaller molecules such as TiO2 that participate in the subsequent cluster formation. Interactions between Ti and O atoms in the cluster stabilize the large structure through the abstraction of water and -CxHy groups