Studies On The Activity And Its Characterization Of Cordierite, Alumina-supported Pd Catalysts For Acetone Oxidation

There are several ways to remove the volatile organic compounds (VOCs), such as absorption, combustion, catalytic combustion and biodegradation. Being have some advantages such as practicability, better removal effect and no secondary pollution caused, the catalytic combustion attracts much more attention. Catalytic combustion is an exclusively effective method for the removal of VOCs, by which toxic VOCs can be completely decomposed into H2O and CO2. Moreover, heat release from the catalytic combustion can also be recycled. Comparing with conventional combustions, catalytic combustion can be performed under lower temperature, saves fuels, and especially, avoids the secondary pollutions caused by NOx that often occurs under higher temperature.There are many kinds of catalysts used in catalytic combustion, generally include noble metal catalysts, transition metal oxide catalysts and rare earth catalysts. Being regarded as one of the most active component, Pd is used widely in catalysts for redox reactions.Because of the favorable oxygen-reserve ability and high performance of anti-ageing, Ce, Zr are often used as assistant catalysts.In this research, Pd(Ce,Zr)/γ- Al₂O₃ /Mg₂Al₄SiO₁8 and catalytic materials were prepared, in which Pd was the active component, γ-Al₂O₃ and Mg₂Al₄SiO₁₈ were carriers. Ce and Zr were used as assistant catalysts. Acetone was employed as target VOC, and its combustion reaction was studied to determine the activities of these catalysts, and the properties of these catalysts were characterized simultaneously.Then under 1000°C, the sample catalysts were forced to be aged for 4 hours to determine the anti-ageing performance of the catalysts.It was found that the concentration of the Pd is the most important factor affecting the catalysts activity, whereas Ce and Zr are the more important factors affecting the catalysts activity. The appropriate concentration of the Pd may make the catalysts have the best activity.Evaluation of aged catalysts indicates that both Ce and Zr have the ability of improving the thermal stabilization of catalysts. After being aged under the temperature of 1000°C for 4 hours, alumina in the catalysts containing Ce and Zr changed its phase from y toy, 5and 9,while alumina in the catalysts without Ce and Zr have the phases of a,8and 0 coexisting .The properties and appearances of the catalysts tested were characterized with XRD, BET and SEM. The results showed that the addition of Ce and Zr changes the structure of the catalysts, and the surface structure of the catalysts was also changed greatly by aging.The effect of Pt on the activitity of Pd catalysts was also studied in this research, the results obtained indicated that less addition of the Pt into the Pd catalysts has almost no effect on its activity.