First-Principles Thermochemistry for the Production of TiO2 from TiCl4

Authors: Richard H. West, Gregory J. O. Beran, William H. Green, and Markus Kraft*

Abstract

Despite the industrial importance of the process, the detailed chemistry of the high-temperature oxidation of titanium tetrachloride (TiCl4) to produce titania (TiO2) nanoparticles remains unknown, partly due to a lack of thermochemical data. This work presents the thermochemistry of many of the intermediates in the early stages of the mechanism, computed using quantum chemistry. The enthalpies of formation and thermochemical data for TiOCl, TiOCl2 , TiOCl3 , TiO2Cl2 , TiO2Cl2 , Ti2O2Cl3 , Ti2O2Cl4 , Ti2O3Cl2 , Ti2O3Cl3 , Ti3O4Cl4 , and Ti5O6Cl8 were calculated using density functional theory (DFT). The use of isodesmic and isogyric reactions was shown to be important for determining standard enthlapy of formation (ΔfH298K) values for these transition metal oxychloride species. TiOCl2, of particluar importance in this mechanism, was also studied with CCSD(T) and found to have ΔfH298K = −598 ± 20 kJ/mol. Finally, equilibrium calculations were performed to identify which intermediates are likely to be most prevalent in the high temperature industrial process, and as a first attempt to identify the size of the critical nucleus.


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Keywords: density functional theory (DFT), gas-phase, homogenous gas-phase combustion, quantum chemistry, thermochemistry, titania,

Associated Projects: Quantum Chemistry and Nanoparticles

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