Influence of calcination temperature and preparation method of TiO2–ZrO2 on conversion of cyclohexanone oxime to ε-caprolactam over B2O3/TiO2–ZrO2 catalyst Original Research Article

The effects of calcination temperature and preparation method of TiO2–ZrO2 mixed oxide on catalytic performance of B2O3/TiO2–ZrO2 catalysts were investigated. TiO2–ZrO2 mixed oxides with the same molar ratio of 1:1 were prepared by co-precipitation method, homogeneous precipitation method, sol–gel method and physical mixing method; each oxide was calcined at a temperature between 110 and 700 °C. Catalytic synthesis of ε-caprolactam from cyclohexanone oxime was evaluated in a fixed-bed flow microreactor at 300 °C and atmosphere pressure. Characterization of catalysts was carried out using adsorption of nitrogen, X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FTIR) and temperature-programmed desorption of ammonia (NH3-TPD) techniques. The experimental results reveal that the calcination temperature in the range of 110–500 °C had only a slight effect on the catalytic performance, but after calcination at 700 °C, the ZrTiO4 crystallite was formed and accounted for the decrease of acidity and catalytic performance. The co-precipitation method provided the catalyst with the highest reactivity while the physical mixing method resulted in the worst catalyst. Catalytic performance of the B2O3/TiO2–ZrO2 catalyst was closely related to its acid strength distributions and pore size.