The Preparation Of Transition Metals/Ceria Based Nanomaterials And Catalytic Performance

Haze has become a serious environmental problem.The pollutants contained in the vehicle exhaust,such as carbon monoxide?CO?,nitrogen oxides?NOx,mainly NO and NO₂?,fine suspended particles and hydrocarbons?HC?,are factors that can not be overlooked.The application of traditional precious metal catalysts were severely restricted due to the high cost,poor stability and poisoning.With the rapid development of nanotechnology,using rare earth catalysts to replace precious metal catalyst has become a new direction of the research.A lot of experimental researches showed that cerium base composite catalysts play superior catalytic properties in CO oxidation reaction and CO+ NO reaction.Based on the above researches,we prepared transition metal/cerium oxide nanomaterials.Meanwhile their structures,morphology and catalytic performance in CO catalytic oxidation reaction and CO+ NO reaction have been studied.In our study,the main contents are as follows:?1?Study on copper-ceria catalysts controlled by chemical precipitation and the catalytic performance for CO oxidationCopper doped ceria porous nanospheres were synthesized using carbon nanospheres as a hard template by a homogeneous precipitation method at low temperature.In the experiment,we selected Ce?NO3?3 as cerium source,Cu?NO3?2 as cooper source,urea as the precipitant,mixture of ethanol and water solution as solvent,to carry out samples with different copper doping concentration?Cu/Cu+Ce=0 to 7.5%mol?.The results demonstrated the morphology transformation from the initial.double-shell spheres to hollow spheres as the doping concentration increased,and the transformation relied on the different temperature ranges which caused the move of carbon template among these samples.Furthermore,the copper-ceria catalysts exhibited enhanced catalytic performance towards CO conversion compared with pure ceria catalysts?e.g.,for the optimal catalysts,the complete conversion temperature was 160?;for the pure catalysts,the complete conversion temperature was 300??.Through the analysis of the catalysts structure,we proved that the superior catalytic performance was derived from a combination of CuOx clusters and copper ions in the Cu-[Ox]-Ce bulk phase.?2?Study on nickel-ceria catalysts controlled by chemical precipitation and the performance on CO+NO reactionIn the experiment,we selected carbon nanospheres as templates,Ce?Ac?3 as cerium source,diethylene glycol?DEG?as solvent,to carry out samples with different nickel content?Ni/Ni+Ce=0 to 20%mol?via a typical solvothermal synthesis,then we obtained CeO₂ nanospheres.We used CeO₂ nanospheres as carrier,selected Ni?NO3?2 as nickel source to prepare nickel-ceria catalysts by a typical chemical precipitation method.Results showed that nickel was highly dispersed over the surface of the cerium oxide,and improve the catalytic performance on the CO + NO reaction?especially when the nickel content was 10%?.Through analysis of the catalysts structure,we proved that the superior catalytic performance was derived from a combination of NiO clusters and copper ions in the Ni-Ce-O structure.?3?Study on M-ceria catalysts controlled by chemical precipitation and the performance on CO+ NO reactionWe used sodium hydroxide solution as solvent,cerium nitrate as cerium source,and prepared CeO₂ nanorods by a typical solvothermal synthesis.Then,we used ceria nanorods as support,selected M?NO3?x as metal source?M=Fe,Co,Ni,Cu,Zr?,prepared M-ceria catalysts via a chemical precipitation method.Results showed that M species can be highly dispersed over the surface of the cerium oxide,and improve the catalytic performance on the CO+NO reaction?especially the Cu-CeO₂ samples?.