TiO2-Catalyzed n-Valeraldehyde Self-Condensation to 2-Propyl-2-Heptenal: Acid Catalysis or Base Catalysis?

Several TiO2 samples with different morphologies and structures, nano/microcomposite of TiO2 (anatase), TiO2 whisker (anatase), and nano-TiO2 (anatase), were prepared and characterized by means of N2 adsorption–desorption, CO2-TPD, and NH3-TPD, and their catalytic performance for n-valeraldehyde self-condensation was investigated. The results indicated that the conversion of n-valeraldehyde was correlated with their acid amount while the selectivity of 2-propyl-2-heptenal was associated with their base amount. Since the catalytic performance of nano-TiO2 (anatase) was the best, its preparation process was further studied and the suitable preparation conditions were obtained. Then the effect of reaction conditions on the catalytic performance of nano-TiO2 (anatase) for n-valeraldehyde self-condensation was investigated and the suitable reaction conditions were obtained as follows: a weight percentage of TiO2 catalyst of 15 wt %, a reaction temperature of 190 °C, and a reaction time of 10 h. Under the above...