Investigation On Preparation Of Nickel-based Catalyst By Adsorption Phase Reactor Technology

Synthesis of NiO/SiO₂ nanocomposite materials in a nanoreactor which formed by the water-rich adsorption layer on the surface of SiO₂ were studied in this dissertation. Ni/SiO₂ catalyst was prepared by aqueous reducing method and the catalystic properties were studied.First the dissertation generalized the characteristic and application of nickel and nickel oxide nanoparticles, and their preparation methods were 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, NiO/SiO₂ nanocomposite materials were successfully prepared by reaction of NaOH with Ni(NO₃)₂ in alcohol-water system. The samples prepared in different methods were compared, it was found that nanoparticles were smaller and more dispersed by adsorption phase reactor technology.Water concentration, reactant concentration and temperature influence the pattern and size of NiO nanoparticles. The author designed a series of experiments including water concentration, reactant concentration and temperature experiments. The influence of these factors to the size and pattern of products NiO were gained with the help of many kinds of analytical methods such as TEM, XRD, Acid & alkali titrate and complexometric titration, 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 nickel nitrate'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 Ni(OH)₂/SiO₂ prepared by adsorption phase reactor technology, nickel catalyst was prepared by aqueous reducing method. The pattern and size of particles were analyzed by TEM and XRD, then catalyzed the reduction of nitrobenzene to aniline by hydrazine.The influence of catalyst quality was firstly studied. It was found that catalytic activity increased with the increase of catalyst quality, and basically unchanged after a certain amount. In order to investigate the influence of Ni loading on catalytic properties, the author compared the two catalysts with different loading for activity and found that catalyst with low-loading of the Ni particles had higher activity. The experiments also showed that chemical adsorption phase was fully formed under 2mL water, the Ni particles was strongly combined with silica surface after reduced, while Ni particles prepared in other water conditions were easily reunited and poor in stability. Ag doping experiments showed that it was contributed to the formation and dispersion of Ni, thereby greatly increased the activity. Different conditions on doping influeneced the particle size and structure of Ni catalysts, thus affected their catalytic properties.At last, the work in the dissertation was generalized, and the problems which still need to discuss in paper were represented.