Alkaline doped TiO2 sol–gel catalysts: Effect of sintering on catalyst activity and selectivity for acetone condensation

In this paper, we prepared by the sol–gel method alkaline titania catalysts, doped by gelling titanium alkoxide with aqueous solutions containing potassium, rubidium or cesium chlorides. XRD patterns showed that samples annealed at 400 and 600 °C contained a single crystalline phase, anastase. Specific surface areas were higher in samples annealed at 400 °C (>100 m2/g) than in those annealed at 600 °C (25 m2/g). The weight density of basic sites determined by CO2–TPD drastically diminished in samples treated at 600 °C. Catalysts were tested for the self-condensation of acetone at 300 °C; main reaction products were isomesityl oxide, mesityl oxide and mesitylene. Samples annealed at 600 °C showed lower acetone conversion rate and low formation of mesitylene than that obtained on samples annealed at 400 °C. It is proposed that the formation of mesitylene occurs via the Michael reaction over the titania support.