Study On The Performance Of Nano-Array Oxide Catalysts Used For Soot Catalytic Combustion

Soot particulates as one kind of the main pollutants in diesel emission havecaused many kinds of environmental issues, such as PM2.5induced air pollution.How to reduce the combustion temperature is significant to the elimination of sootemission. Up to now, the catalytic combustion technique is regarded as the mostpotential and efficient after-treatment technology for soot removal. In this thesis, innanoscale, specific microscopic morphology and structure of catalysts were designedbased upon the requirements of this reaction system. A series of nano array basedoxides catalysts were synthesized and used for soot oxidation.Firstly, we conducted a series of exploratory experiments. The different1-D CuO array-structured catalysts were fabricated on Cu foil by different reactionconditions. Then the influence of morphology on the catalytic activity was studied.Among the catalysts we synthesised, the vertically arranged CuO nanorods thatprepared by calcination of Cu foil at high tempreture exhibits the most excellentperformance. As compared with CuO powder catalyst, this sample also showed bettercatalytic performance. In addition, CeO2nanoparticles were supported on CuOnanorods to further improve the catalytic activity.To overcome the gathering of soot in the blank area among CuO nanorods (about300nm between two nearby nanorods), we designed a kind of domain-confinedmacroporous TiO2-nanotube to replace nanorod catalyst. The vertically orientedTiO2-nanotubes with the pore diameter around140nm were prepared. Through suchdesign, the soot particulates falling into the macroporous structure of TiO2-NA will beconfined in a limited space and have more opportunities to contact with active sites.Forthermore, the active component Co3O4nanocrystals were anchored into the innersurface of TiO2-NA by three different methods. For comparison, the conventionalsamples of TiO2powder and its supported catalyst were also employed for sootcatalytic combustion. It is found that the TiO2-NA based catalyst exhibited muchhigher activity than the powder catalyst owing to its larger accessible specific surfacearea and higher soot-catalyst contact efficiency, especially the sampleCo3O4/TiO2-NA(SG) synthesized through surface-grafting method. However, thenanotube is too long, which makes the amount of the loaded active Co species is verylimited. Finally, in order to overcome the shortcoming of the former system, the compactFe2O3nanorods catalyst on Ti foil was prepared by hydrothermal method, by a simpechemical bath deposition (CBD) Co3O4nanoparticles were loaded on Fe2O3nanorods.The effects of different loadings on the structure and soot combustion activity weresystematically investigated. It is found that the compact Fe2O3nanorods arrayexhibited a higher catalytic activity than Fe2O3powder. Moreover, when Co wasloaded on Fe2O3nanorods, the activity is further improved. The catalyst with propercontent of Co3O4shows the best activity due to the much smaller crystallite size andmore uniform distribution of Co species.