Preparation Of Highly Efficient Pd Nanocatalyst And Its Performance In CO Oxidation At Low Temperature

CO oxidation is important in heterogeneous catalysis field for both fundamental studies and environmental applications. It is necessary to remove CO from CO2 laser, protective mask, sealed cabins, hydrogen for proton-exchange fuel cell and etc. Meanwhile, CO oxidation is also used as a model reaction to study the catalyst structure, adsorption/desorption, redox ability, and reaction mechanism.Nobel Pd catalyst has attracted much attention due to its effective performance in CO oxidation at low temperatures. It is widely believed that the structure and dispersion of Pd particles, the mophology of support, and the preparation method influence the activity. In addition, to enhance the thermal stability and sinter-resist capacity of Pd nanoparticles in chemical reaction remains a hot research topic.In this thesis, taking Pd nanoparticle as active center and CeO2 nanotube as the support, we herein prepared two kinds of novel nanotube-structure catalysts including supported and core-shell nano Pd catalysts. They were investgated in CO oxidation. The results show:1. The supported nano Pd catalyst with CeO2 nanotube as the support shows highly efficient activity in CO oxidation at low temperatures. When the volume ratio of CO and O2 is 1:4 and the gas hourly space velocity is 12000 mL·gcat-1·h-1, the catalyst can convert CO completely at 100℃, wich is much more active than the one with commercial CeO2 as support.2. The core-shell nano catalyst is prepared by deposition of Pd nanoparticles on CeO2 nanotube and coating SiO2 as shell. It shows good activity in CO oxidation at low temperatures and converts CO completely at 140℃ under the same reaction conditions above. Compared with the supported nano Pd catalyst without SiO2 shell, the core-shell nano catalyst has a slight decrease in activity, but shows a better thermal stability. After the stability experiment with aging treatment at 700℃, the core-shell nano catalyst is structurallly stable. The size of Pd nanoparticles almost keeps the same and the activaty remains steady. In contrast, Pd nanoparticles on the supported nano catalyst show up migration and aggregation, leading to a remarkable deactivation.