TiO2-ZrO2 Composite Oxide as an Acid-Base Bifunctional Catalyst for Self-Condensation of Cyclopentanone

TiO2-ZrO2 mixed oxides TZ-SG and TZ-ST were synthesized by a sol-gel method and a solvothermal method, respectively. The physicochemical properties of the TiO2-ZrO2 mixed oxides were characterized by X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, pyridine Fourier transform infrared spectroscopy, NH3-temperature-programmed desorption (TPD), CO2-TPD, and N-2 adsorption-desorption isotherms. The prepared TZ-ST was a stable and high-efficiency catalyst that combined the advantages of acidic and basic solid catalysts for cyclopentanone self-condensation. Compared with TZ-SG, TZ-ST exhibited higher catalytic activity in cyclopentanone self-condensation because of its high specific surface area and plentiful acid-base sites. In addition to its basicity, the acidity of TiO2-ZrO2 also had an important influence on its catalytic activity for cyclopentanone self-condensation. Under optimum reaction conditions (a catalyst/cyclopentanone mass ratio of 0.2:1, a reaction temperature of 140 degrees C, and a reaction time of 6 h), the dimer (C-10) yield could reach 75.6% on TZ-ST.