| Volatile organic compounds have become important components of atmospheric pollutants and catalytic oxidation technology is an effective and widely used method for the treatment of them.Pt based catalysts are considered to be one of the most promising catalytic materials because of their high catalytic activity and good selectivity.The emphases and difficulties of current research lie in reducing the loading of Pt and improving the stability of the catalysts in the premise of high catalytic activity.The use of transition metal oxides?MOx?as“active supports”can not only allow Pt to be uniformly dispersed on the surface,but also induce interaction between the support and Pt which is advantageous for enhancement of catalytic activity and stability.Therefore,in order to obtain Pt based catalysts with excellent catalytic performance and low loading,Pt/MOx catalysts were prepared in this dissertation by liquid phase reduction using different metal oxides?MnOx,NiOx,FeOx,etc.?as supports.And a bi-component of manganese oxides supported Pt catalyst?Pt/MnO2@Mn3O4?was also synthesized.The effect of the oxides supports on the activity as well as the relationship between performances of toluene catalytic oxidation and interfacial structure as well as Pt—MnO2@Mn3O4 interaction were investigated.Detailed research contents and results include:1.Different metal oxide supports?NiO,Fe2O3,MnO2 and CuO?were prepared,and a series of Pt/MOx catalysts were synthesized via the liquid-phase reduction method.Through characterization analysis and activity tests,it was found that the difference of compositions of oxides supports in Pt catalysts would cause the distinction of activity,which results from Pt species having different activation abilities of gas-phase oxygen.And the catalyst prepared by using manganese oxide as support possessed the highest toluene catalytic activity,over which the complete conversion temperature is about 170 oC.2.The effects of different manganese oxides supports on the performance of Pt based catalysts were investigated.The results showed that the bi-component MnOx supported Pt catalyst?Pt/MnO2@Mn3O4-I?through in situ synthesis had excellent catalytic performance with low Pt loading?0.25 wt.%?.And its activity was significantly higher than Pt/MnO2 and Pt/Mn3O4,supports of which were single manganese oxide.Through characterization analysis,it could be found Pt/MnO2@Mn3O4-I had higher proportion of Pt0 and owned good interaction of Pt and the support.And surface Pt species could activate O2 to react with toluene more easily,so the catalyst had better activity and could completely oxidize toluene between 150160oC.Compared with the catalysts in other literatures,the sample still showed obviously more outstanding activity,further indicating its excellent catalytic oxidation ability.3.The in situ synthesized Pt/MnO2@Mn3O4-I catalyst had unique three-phase?Pt,MnO2@Mn3O4?interfacial structure,and this interface structure was closely related to the performance of catalyst.The support of Pt/MnO2@Mn3O4-T sample prepared by two steps also contained MnO2 and Mn3O4,while no three-phase interface existed in this sample.Compared with Pt/MnO2@Mn3O4-T,Pt/MnO2@Mn3O4-I had fine metal-support interaction at the interface which improved the sticking coefficient of O2 and enhanced the ability of dissociated adsorption of O2.And the presence of special interfacial structure and interaction was conducive to the formation of Pt0 and made the gaseous oxygen more susceptible to be activated by the catalyst.These properties resulted in Pt/MnO2@Mn3O4-I with low Pt loading exhibited excellent catalytic activity and high stability and water resistance. |
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