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

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 Ti–O bonds at high temperatures. Ti₂O_xC_yH_z species appear earlier than TiO₂ during TTIP pyrolysis, while TiO₂ forms earlier than Ti₂O_xC_yH_z 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 Ti–O bond with TiO_xC_yH_z species or titanium clusters followed by continuous breakage of Ti–O or C–O bonds to release hydrocarbon moieties.