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dc.contributor.advisor Wong, Michael S.
dc.creatorSoultanidis, Nikolaos
dc.date.accessioned 2013-03-08T00:39:08Z
dc.date.available 2013-03-08T00:39:08Z
dc.date.issued 2012
dc.identifier.urihttps://hdl.handle.net/1911/70448
dc.description.abstract Supported metal oxides (SMOs) are important catalytic materials that find numerous applications in important industrial processes. Improving the structural properties of SMOs is a challenging objective due to material synthesis and characterization limitations. Recent developments in the characterization of SMOs, specifically tungstated zirconia (WO x /ZrO 2 ), have revealed structural information that renewed scientific interest in developing more sophisticated synthetic protocols for SMOs. The current work aims to provide a robust characterization of WO x /ZrO 2 by using different characterization techniques and probe reactions. Conventional and non-conventional synthetic methods are investigated to cover the whole spectrum of published methods in order to understand the properties and limitations of these techniques. In the second part of this work, a new synthetic approach is presented that successfully produces ultrasmall (smaller than 2 nm) tungsten oxide nanoparticles (WO x NPs). By using conventional tungsten precursors and oleylamine, WO x NPs are synthesized, characterized, and finally supported to test their propene metathesis activity. Conventional WO x /ZrO 2 catalysts were prepared and extensively studied by probing their n -pentane isomerization activity and methanol dehydration activity. WO x /ZrO 2 prepared via incipient wetness impregnation shows maximum n -pentane isomerization turnover rates ( TOR ) at intermediate surface densities ( � surf ). This method delivers the most active n -pentane isomerization WO x /ZrO 2 catalysts since it maximizes the number density of the active sub-nm slightly distorted Zr-WO x sites at � surf between 5.2-6.2 W/nm 2 . By comparing the n -pentane isomerization activity with the methanol dehydration activity of WO x /ZrO 2 , n -pentane isomerization is shown to be an excellent probe reaction for qualitatively identifying the relative (to the other species) population density of Zr-WO x clusters. Bimolecular n -pentane isomerization is the prevailing mechanism and requires a higher population density of Zr-WO x clusters than methanol dehydration. In the second part of this work, a new solvothermal synthesis route for the preparation of ultrasmall tungsten oxide nanoparticles (WO x NPs) is introduced. By using ammonium polyanionic salts and oleylamine, high yields (92±5%) of oleylaminecoated WO x NPs were consistently synthesized. The co-addition of an organic oxidant during the synthesis led to smaller WO x NPs thereby providing insight into the NP synthesis mechanism. Deposition and activation of the NPs on SiO 2 support by removal of oleylamine allows better control over the WO x domain size than conventional methods. Oleylamine suppresses WO x NP sintering during calcination and prevents the formation of larger polytungstates present in conventional catalysts. The supported WO x NPs were found to be up to 3 times more selective for metathesis products than conventionally prepared tungstated silica likely due to their controlled structure.
dc.format.extent 230 p.
dc.format.mimetype application/pdf
dc.language.iso eng
dc.subjectApplied sciences
Metal oxides
Tungsten oxide
Zirconium oxide
Supported metal oxides
Chemical engineering
Materials science
dc.title Solvothermal Synthesis and Supported Catalysis of Polyanion-derived Metal Oxide Nanoparticles
dc.identifier.digital SoultanidisN
dc.type.genre Thesis
dc.type.material Text
thesis.degree.department Chemical and Biomolecular Engineering
thesis.degree.discipline Engineering
thesis.degree.grantor Rice University
thesis.degree.level Doctoral
thesis.degree.name Doctor of Philosophy
dc.identifier.citation Soultanidis, Nikolaos. "Solvothermal Synthesis and Supported Catalysis of Polyanion-derived Metal Oxide Nanoparticles." (2012) Diss., Rice University. https://hdl.handle.net/1911/70448.


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