Acetone gas phase condensation on alkaline metals doped TiO2 sol-gel catalysts

The vapor-phase condensation of acetone was studied over sol-gel prepared TiO2 and TiO2-doped with 1 wt.% of Li+ or Rb+. The acetone condensation was catalyzed by basic sites and the obtained products were mesityl oxide (MO), isomesityl oxide (ISMO), mesitylene (M) as well as isophorone (IP) and phorone (P). The TiO2 crystalline structure was characterized by XRD and the basicity of catalysts by means of CO2 chemisorption. The number of basic sites was 0.057 mmol CO2/g for TiO2 and Rb/TiO2 and 0.676 mmol CO2/g for Li/TiO2 catalyst. CO2-TPD showed that the strongest of the basic sites follows the order Rb/TiO2 > TiO2 > Li/TiO2. Activity was found of the same order in the three catalysts. Selectivity patterns shown that MO (70%) was the main product in Li/TiO2 while for TiO2 and Rb/TiO2 comparable amounts of MO (41 and 44%) and M (39 and 39%) were obtained.