Construction Of Titanium Dioxide-Based Paper Catalyst And Its Synergistic Catalytic Effect On Soot

With the rapid development of economy,the number of motor vehicles is increasing,and particulate matter（PM）emissions account for more than 99%of the total vehicle emissions.The upgrading and innovation of the particle filter（DPF）of the tail gas post-treatment device is particularly important.Paper-based catalysts have the advantages of simple production,low price,high porosity and good gas diffusivity.The interwoven structure of the fiber provides a good reaction site for the loading of active components and the catalysis of particulate matter.Titanium dioxide has excellent electronic properties and thermal stability.As a catalyst matrix,it has a very important prospect.In this thesis,a paper-based catalyst for titanium dioxide-based composite fibers was prepared.By loading multiple active components,a paper-based catalyst with excellent mechanical properties,catalytic activity and stability was prepared.X-ray powder diffraction（XRD）,H₂ temperature-programmed reduction（H₂-TPR）,CO₂temperature-programmed desorption（CO₂-TPD）and other means were used to study the structural design path of titanium dioxide-based high-efficiency paper-based catalysts from the perspectives of active components,matrix fibers and molding processes.The results are as follows:Firstly,K,K-Cu and K-Mn supported TiO₂-ZrO₂ paper catalysts were prepared,and the effects of calcination temperature and active components on the induced phase separation mechanism were investigated.The experimental results show that the single K-supported catalyst will generate potassium titanate whiskers on the surface of the fiber with the increase of the preparation temperature,and the thermal stability is improved.The K-Cu and K-Mn supported catalysts produce potassium octatitanate with excellent stability as the temperature changes.The catalytic activity and thermal stability are attributed to the synergistic catalytic effect between Cu,Mn oxides and potassium octatitanate.The theoretical activity will be greatly reduced after free potassium enters the lattice at high temperature to form potassium octatitanate,but the good synergistic catalytic effect between transition metal oxide and potassium octatitanate will make up for the lack of activity in this part,and the stability of confined potassium increases the service life of the catalyst.Secondly,K/TiO₂-CeO₂ and K/TiO₂-SiO₂ catalysts were prepared by changing the composition of the matrix fiber,and TiO₂-ZrO₂ fibers with different titanium-zirconium ratios were loaded on 15K5Cu to analyze the effect of the change of the composition on the induced phase separation mechanism.The results show that the phase separation product of K/TiO₂-CeO₂ is potassium tetratitanate.The surface exposure of potassium tetratitanate can activate the lattice oxygen provided by cerium dioxide,and there is a good synergistic effect between the two.The K/TiO₂-SiO₂ catalyst exhibits catalyst activity only in the presence of free potassium.The potassium octatitanate formed after phase separation exhibits its own high stability and chemical inertness.The change of titanium-zirconium ratio will also affect the formation of potassium octatitanate,which indicates that the synergistic effect between the active component and the support is crucial in the catalytic reaction.The molding process can regulate the structure of the thesis catalyst.The foam molding process is used to prepare the thesis catalyst.By adjusting the foaming agent concentration and stirring speed,the effects of foam distribution and foam stability on the molding structure of the thesis catalyst are observed.It was found that the foam size distribution of 5 g/L polyvinyl alcohol solution and 3000 r/min stirring speed was uniform and the foam stability was moderate.By loading the same active component,the soot catalytic activity(T₅₀)can be reduced by 10～20℃ compared with the traditional wet-laid thesis catalyst.