Preparation Of Cordierite-supported Three-dimensional Macroporous Manganese-based Monolithic Catalysts And Their Catalytic Performance For Soot Combustion

Air pollution has a serious impact on human health.Motor vehicle exhausts are one of the main factors of air pollution.In the future,diesel vehicles will still be an indispensable part of China’s road transportation.Compared with nitrogen oxides,hydrocarbons and carbon monoxide,which have relatively mature elimination methods for gas phase pollutants,diesel soot particulate matter（PM）lacks more effective catalytic purification post-treatment technology.Therefore,PM elimination is an important research direction in environmental protection.Considering that the reaction between PM and O₂（or NOx）on the catalyst is a gaseous（NO,O₂）-solid（catalyst）-solid（PM）heterogeneous catalytic reaction,the construction of three-dimensionally macroporous structure can increase the contact efficiency of PM and catalyst.In this thesis work,monolithic catalysts with three-dimensional macroporous Ce_0.5Zr_0.5O₂coating were prepared via the modification of Ce O₂with doping of Zr.The effects of different preparation methods and loading of transition metal oxides on the catalytic removal of soot particle were investigated.The morphology and physicochemical properties of the monolithic catalysts were investigated by means of SEM,XRD and Soot-TPR.And the catalytic performances for soot combustion reaction on the series of as-prepared monolithic catalysts were investigated.The main research results of this thesis work are as follows:（1）The cerium zirconium oxide coating layer with three-dimensionally macroporous morphology was prepared by colloidal crystal template method and one-step dipping method.The morphology of the prepared coating layer was characterized by SEM and BET techniques.It was found that the coating of Ce_0.5Zr_0.5O₂had a large specific surface area.Among them,16%Ce_0.5Zr_0.5O₂/cordierite monolith catalyst gave the best catalytic activity,and its T₁₀,T₅₀and T₉₀were 252℃,420℃and499℃,respectively.（2）A series of three-dimensionally macroporous structure Mn Ni O_x/Ce_0.5Zr_0.5O₂/cordierite monolith catalysts were successfully prepared by colloidal crystal template method.The existence of the structures of coating layer and active components increases the specific surface area of the catalyst by 3～6 times.The effects of different concentrations of Mn-Ni solution on the catalytic performance of the as-prepared Mn Ni O_x/Ce_0.5Zr_0.5O₂/cordierite monolith catalysts for soot combustion were investigated.It was found that 4%Mn Ni O_x/Ce_0.5Zr_0.5O₂/cordierite monolith catalyst showed the best catalytic performance for soot combustion.The T₅₀value increased only by 44°C after 7 cycles of testing,indicating that the catalyst has good cyclability.（3）A cerium-zirconium metal oxide coating layer with three-dimensional macroporous morphology was successfully prepared on the surface of cordierite by a one-step impregnation method,which increased the specific surface area of the monolith catalyst by three times.The catalytic activities of manganese-based bimetallic oxide monolith catalysts were investigated by doping with different transition metals.Among them,the Mn Ni O_x/CZO/cordierite monolith catalyst showed excellent catalytic performance for soot combustion and water resistance.