Doctor of Philosophy (PhD)
The research in this dissertation focuses on the synthesis of size-controlled metal oxide nanoclusters (< 10 nm) on amorphous silica and their catalytic performance in thermal degradation of chlorinated benzenes with regard to the cluster size effect. Furthermore, with the concern that metal can condense as the nano-size nuclei core for particle growth in combustion process, a flow reactor was built to investigate the effect of metal oxide nanoparticles on the formation of soot in fuel-rich combustion. The synthesis of copper oxide nanoclusters was carried by calcination of silica impregnated with dendrimer-metal complexes. The 4th generation poly(propylene imine) dendrimer DAB-Am32 was used in this template-based method. The sizes of copper oxide nanoclusters were exquisitely controlled in the range of 1-5 nm with narrow size distribution by changing the stoichiometric ratio of metal ion to the terminal primary amines of dendrimer, the equivalent metal oxide loading on surface, and the impregnation procedure. XANES and XPS studies revealed that CuO was the dominant component of copper oxide nanoclusters. This method was also experimentally proven to be valid in the preparation of other metal oxide nanoparticles, e.g., Ni and Fe, and with other oxide substrates, e.g., titanium oxide. Chlorinated benzenes were selected as the model compound for studying the activity of metal (Cu and Fe) oxide catalysts with regard to their cluster sizes. Compared to the surrogate of coarse metal oxide samples, which was prepared by incipient wetness method, their nanosize analogues showed superior catalytic activity on the conversion of chlorinated benzenes under both pyrolytic and oxidative thermal condition. Furthermore, such catalytic size effect was also observed on the selectivity of products yields. Sooting combustion was performed using a two-zone flow reactor with precise control on experimental parameters. Gas suspended metal oxide nanoparticles were generated by burning off the organic backbone of the dendrimer-metal complexes in zone 1 and immediately transferred to zone 2, where the hydrocarbon combustion occurred. TEM results of the particulate sample collected at the outlet of reactor indicated that metal oxide nanoparticles promoted soot formation. GC/MS analysis of the extracted organic materials from soot samples suggested the formation of PAH was also promoted by metal addition as well.
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Wu, Hongyi, "Size Controlled Metal Oxide Nanoparticles:Synthesis, Characterization, and Application to Catalysis" (2009). LSU Doctoral Dissertations. 1442.
Dellinger, Barry H