A Study Of Sea Urchin-like Transition Metal Catalysts For Catalytic Soot Elimination

Diesel vehicles are widely used in transportation because of their advantages of low cost and high fuel efficiency.However,the soot particles produced in the tail gas pose a great threat to the natural environment and human health.At present,the combination of diesel engine particle trap and catalyst is considered to be one of the most promising methods for the elimination of diesel soot particles.However,due to the low contact efficiency between the catalyst and the soot particles,the high temperature required for catalytic oxidation of soot,and the lack of efficient catalysts,the development of this technology is restricted.Recently,transition metal oxides have been widely concerned about their excellent redox properties due to their general valence.Therefore,in this study,the transition metal catalyst with sea urchin morphology was used as the base,and potassium carbonate was loaded on the catalyst with sea urchin morphology by simple impregnation method.The transition metal sea urchin catalyst has a low ignition temperature and exhibits a good soot catalytic combustion activity.At the same time,we used XRD,SEM,HRTEM,FT-IR,XPS,H₂-TPR,Soot-TPR and other characterization results to reveal the reason of catalyst activity enhancement,and proposed the possible reaction mechanism.This paper provides a catalyst preparation strategy,which provides a new way for the design and construction of efficient diesel soot combustion catalyst.1.In this paper,a single metal sea urchin-like Fe₂O₃ catalyst(Fe₂O₃ US)was synthesized by hydrothermal synthesis.Compared with the granular catalyst(Fe₂O₃NP),it showed good catalytic performance.The sea urchin-like catalyst(K/Fe₂O₃ US)supported by impregnation method showed high catalytic activity compared with Fe₂O₃US.The K/Fe₂O₃ US catalyst can still maintain excellent catalytic performance after four active cycle tests.This is mainly because:(1)Sea urchin structure can improve the contact efficiency between catalyst and soot particles,and at the same time improve the content of reactive oxygen species.(2)The interaction between potassium species and iron increases the content of reactive oxygen species and improves the redox performance of the catalyst.2.Sea urchin-like NiO-NiCo₂O₄ catalyst(NiO-NiCo₂O₄US)was synthesized by hydrothermal method.The sea urchin-like NiO-NiCo₂O₄ catalyst(NiO-NiCo₂O₄ US)showed excellent catalytic activity compared with the granular catalyst(NiO-NiCo₂O₄NP),NiCo₂O₄ US and Ni O US catalyst.The sea urchin-like NiO-NiCo₂O₄ catalyst(K/NiO-NiCo₂O₄US)prepared by impregnation with potassium showed higher catalytic activity than that of NiO-NiCo₂O₄US at the ignition temperature of 307?.The K/NiO-NiCo₂O₄US catalyst exhibited excellent stability after five cycles of activity tests.The high catalytic activity and stability are mainly attributed to the following two reasons:(1)Sea urchin structure can improve the contact efficiency between the catalyst and soot particles,and produce more reactive oxygen species.(2)The interaction between potassium species and Ni-Co metal increases the content of reactive oxygen species and improves the redox performance of the catalyst.Meanwhile,the synergy between Ni O and Ni Co₂O₄ also promotes the reaction.