A reactive force field molecular dynamics study on the inception mechanism of titanium tetraisopropoxide (TTIP) conversion to titanium clusters

Abstract

We performed ReaxFF reactive molecular dynamics simulations to investigate the inception mechanism of TTIP precursor droplet conversion to Ti-containing clusters in 1000 K–2500 K with or without gaseous O2 molecules. A new Ti/C/H/O ReaxFF force field has been developed. Key intermediate titanium species and the initial decomposition pathways of TTIP are identified. The effects of temperature, O2 concentration and high-temperature residence time on the conversion of TTIP to incipient titanium clusters are investigated. Results suggest that high pyrolysis temperature does not necessarily promote the formation of incipient Ti-containing clusters, due to less stable TiO bonds at high temperatures. Ti2OxCyHz species appear earlier than TiO2 during TTIP pyrolysis, while TiO2 forms earlier than Ti2OxCyHz species and has much higher concentration with ambient O2. Decreasing high-temperature residence time boosts the formation of Ti-containing clusters by facilitating the condensation of TiO2 vapors. The growth pattern of the incipient titanium clusters is elucidated as formation of TiO bond with TiOxCyHz species or titanium clusters followed by continuous breakage of TiO or CO bonds to release hydrocarbon moieties.