Technical Report 55, c4e-Preprint Series, Cambridge

Authors: Richard H. West, Raphael Shirley, Markus Kraft*, C. Franklin Goldsmith, and William H. Green

Reference: Technical Report 55, c4e-Preprint Series, Cambridge, 2008

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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. (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 pressuredependent rate expression for the reaction TiCl₃ + O₂ = TiO₂Cl₃ is found using VTST, a stable Ti₂O₂Cl₆ species is located on the minimum energy pathway for TiCl₃ + TiO₂Cl₃ = 2 TiOCl₃, and a number of new elementary reactions are added. Thermochemical data are provided for Ti₂O₂Cl₆, Ti₂O₂Cl₅ and TiCl₂OCl. 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, to investigate the influence of PFR temperature on particle size distributions. The extension of the PBM to track primary particles allows creation of TEM-style images from the simulation and first results are presented.

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