Surface and bulk reactions of carbon tetrachloride with titanium dioxide

Two different reactions occur between CCl₄ and TiO₂. At moderate temperature, the nature of the superficial reaction strongly depends on the hydration state of the solid. On a dry titanium dioxide, CCl₄ chemisorption on two bridges Ti-O-Ti gives a carbonyl complex detected by infrared spectroscopy. The reaction which follows from destruction of this complex proceeds by exchange of two superficial oxygen atoms for four chlorine atoms, with formation of gaseous CO₂. Strongly oxidizing Ti⁴⁺ ions, with high electron accepting properties, are created through the elimination of superficial oxygen atoms. On hydrated titanium dioxide, these reactions are followed by the formation of HCl which generates hydronium ions. Results obtained on TiO₂ and γ alumina point out the high reactivity towards CCl₄ of superficial oxygen atoms, compared to hydroxyl groups. Reticular reaction, which starts at 150°, is a proof of the relatively high mobility of the oxygen in the anatase lattice.