Studies On Preparation And Properties Of Pd Nanocatalyst By Adsorption Phase Reactor Technology

Synthesis of Pd/SiO₂ nanocomposite materials in a nanoreactor which formed by the water-rich adsorption layer on the surface of SiO₂ were studied in this dissertation. Pd/SiO₂ catalyst was prepared by ethanol partially reducing method and the catalystic properties were studied.First the dissertation generalized the research progress of the chlorinated organic compounds dechlorination methods. The characteristic and application of Pd catalyst was simply introduced. Based on the generalization of research that had been done, the dissertation's research orientation and experiment strategies were proposed.Based on the adsorption phase reactor technology, Pd/SiO₂ nanocomposite materials were successfully prepared by reaction of NaOH with PdSO₄ and partial reduction in alcohol-water system. The influence of these factors to the size and pattern of products Pd were gained with the help of many kinds of analytical methods such as TEM, XRD, and some rules were gained:When water concentration was low, reaction mainly happened in chemical adsorption phase, in which the velocity was relatively low, the reactant concentration mainly influenced on this situation. When water concentration increased, physical adsorption phase formed gradually, the reaction was relatively fast in this phase, and was controlled by the velocity of Pd cation 's diffusion. Reaction quickened up as the temperature increased. However, the adsorption phase was destroyed when temperature was too high, and reaction happened in bulk phase.Based on Pd(OH)₂/SiO₂ prepared by adsorption phase reactor technology, Pd catalyst was prepared by ethanol reducing method. The pattern and size of particles were analyzed by TEM and XRD, then catalyzed the hydrodechloriation of p-chloroaniline to aniline. The influence of catalyst precursor was firstly studied. It was found that catalytic activity was the same with different precursor. In order to investigate the influence of Pd loading on catalytic properties, the author compared the two catalysts with different loading for activity and found that the grain size of catalyst with high-loading of the Pd particles is larger, and catalyst is better in stability. The experiments also showed that chemical adsorption phase was fully formed under 1mL water, the Pd particles was strongly combined with silica surface after reduced, while Pd particles prepared in other water conditions were easily reunited .At last, the work in the dissertation was generalized, and the problems which still need to discuss in paper were represented.