Hydrothermal Synthesis Of Halide-doped Titania Nanofiber And Its' Base Catalytic Properties

One-dimensional nano material or nanofiber, which combines the functions of nano material and the ease of separation after reaction, has special charmings in application as catalysts or supports. This thesis Degussa P25 titania was taken as the raw material for hydrothermal synthesis of the ion-exchangeable titanate nanofiber, which was further modified and tested as a novel base catalyst. After screening of the proper conditions for synthesis of the titanate nanofiber, the control of pore structure and morphology of the nanofiber was probed in the first place. As illustrated by SEM and TEM pictures, the hollow titanate nanofibers featured by external diameter 10 ~ 40 nm and 2~3nm pore size can be produced after treating TiO2 with 10 ~ 15 M NaOH at 70 ~ 130oC for around 24h. It was found that with the addition of certain organic reagents, the originally hollow nanofibers became solid; while the diameter and length of the fibers can be controlled by adjusting the synthesis temperature, which would induce the change of BET surface area by times. Later, the solid nanofibers were modified by halide doping and cation exchange and the basicity of which were tested in reactions of alcoholysis and transesterification, respectively. In alcoholysis reaction study, the influence of doping component and amount, calcination temperature and alcoholysis reaction temperature were investigated. The catalyst stability tests were carried out with the reason of deactivation analyzed and the regeneration method examined. Among the catalysts, NaF doped nanofibers calcined at 400oC has the highest activity, and the main reason of catalyst deactivation is carbon deposition. The activity can be partially resumed by calcination in air at 400 oC. The CO2 temperature programmed desorption test for the most active catalyst illustrated that the surface was dominated by base sites of medium strength, and the amount surpassed that found in CaO. The reaction results of transesterfication proved that after exchange of different cations, the activity of catalyst can be enhanced obviously, and the best catalyst was exchanged by Ca:Zn in the ratio of 1:4. The above research have paved the way for the application of this new material in the catalysis field.