Abstract:Ti-Zr-O oxide were prepared by coprecipitation with zirconium nitrate and tebutyl titanate and then they were used as supports to prepare Mn/Ti-Zr catalysts by impregnation method. The catalysts were characterized by XRD, N2 physical adsorption, H2-TPR, NH3-TPD, and TG-DTA. The effects of the composition and structure of catalysts, as well as reaction conditions on the performances in methyl benzoate (MB) hydrogenation, as well as catalyst lifespan, deactivation, and regeneration of Mn/Ti-Zr catalysts were investigated. The results indicated that when TiO2 content and Mn loading in Ti-Zr-O support were12% and 8% (based on the mass of Ti-Zr-O oxide, the same below), the prepared catalyst had the best properties. This catalyst produced a high MB conversion of 98.0% and an integrated selectivity of benzaldehyde and benzyl alcohol at 89.7% under the optimized reaction conditions [T = 390℃, p = 1.0 MPa，n(H2)∶n(MB) = 9∶1 and weight hourly space velocity (WHSV) = 0.5 h-1). The activity and selectivity of Mn/Ti-Zr catalysts in the hydrogenation of MB were are related to the redox behavior of MnOx species on the surface of Mn/Ti-Zr and the acidity of the catalysts. Besides, the catalyst exhibited excellent structural stability with about 11% loss in activity after reaction for 1000 h due to deposition of heavy molecules and coke on its surface. The slightly deactivated catalyst could recover its initial activity and selectivity by simple calcination.
