Non-thermal Plasma Assisted Au/CeO₂ Catalysis For Soot Combustion

The aerodynamic equivalent diameter of diesel particulate matters is so small as to be easily inhaled and do great harm to human health. Carbonaceous fractions, which is also called soot, accounts for large percentage of the PM. Soot consists mainly by primary particulars of carbon, and can be removed by oxidation. While the temperature range of diesel engines are too low to allow the combustion of soot, we adopt the catalysts to reduce the reaction temperature of soot oxidation. Non-thermal plasma will introduce a large amount of highly active radicals under low temperature, thus to realize highly efficient clearing. In combination of the advantages of both catalysis and NTP, the NTP assisted catalysis for soot combustion has been highly valued.We intend to develop a kind of catalyst which shows good catalytic oxidation performance for carbon black. To study the characteristic temperature difference for carbon black combustion brought by different preparation conditions. And we also study the efficiency of NTP assisted catalysis for soot combustion. After all these works, some specific conclusions in this work are drawn as follows:(1) Au/CeO2 catalysts are prepared by co-precipitation method. The synthesized catalysts make the characteristic temperatures (i.e. Tio and Tm) of soot oxidation obviously decrease, and the activation energy of reaction decrease as well. Among all the cataysts prepared, AuCe12h shows the lowest characteristic temperatures -- Tio 334℃ and Tm 481℃, which is made under the condition that gold content 2wt%, precipitation temperature 70℃, drying time 12h and calcination temperature 400℃.(2) Au/CeO2 catalyst enhanced the selectivity of CO2 production, as well as the formation rate of CO2. When the temperature is 200℃, the intensity of characteristic peak height at 2360cm-1 of CO2 IR spectrum is about 18 times of the one without catalyst.(3) We designed and built the set-up of DBD-catalysis reactor, to study the NTP assisted catalytic removal of carbon black. By comparison of the IR spectra of the outlet product with and without plasma, we find out that NTP increased the CO2 formation rate. In the meanwhile, there brought in the by-products like ozone and NOx. We also studied the plasma-pretreated catalyst of Au/CeO2. It shows that the characteristic tempeture of carbon black oxidation decreased as T10 334℃->318℃, Tm 381℃->370℃. This may be caused by the change of catalyst brought by NTP process, which increased the amount of active oxygen species on the catalyst surface.