A detailed kinetic model for combustion synthesis of titania from TiCl4

The combustion of TiCl4 to synthesize TiO2 nanoparticles is a multimillion tonne per year industrial process, the fundamental details of which are still not known. The gas-phase kinetic model presented by West et al. [R.H. West, M.S. Celnik, O.R. Inderwildi, M. Kraft, G.J.O. Beran, W.H. Green, Ind. Eng. Chem. Res. 46 (19) (2007) 6147–6156] is improved upon using density functional theory (DFT) and variational transition state theory (VTST) calculations. The pressure-dependent rate expression for the reaction TiCl3 + O2⇌⇌ TiO2Cl3 is found using VTST, a stable Ti2O2Cl6Ti2O2Cl6 species is located on the minimum energy pathway for TiCl3+TiO2Cl3⇋2TiOCl3, and a number of new elementary reactions are added. Thermochemical data are provided for Ti2O2Cl6Ti2O2Cl6, Ti2O2Cl5Ti2O2Cl5 and TiCl2OClTiCl2OCl. The new kinetic model is used to simulate a rapid compression machine (RCM) and a plug flow reactor (PFR) described in the literature. Agreement with the RCM measurements is good, but simulations of the PFR are less satisfying, suggesting that surface deposition on the reactor walls may have dominated these measurements, which have been the basis of many theoretical models. Finally, the gas-phase kinetic model is coupled to a particle population balance model (PBM) incorporating inception, coagulation, growth, and sintering.