Defense Date

2005

Document Type

Dissertation

Degree Name

Doctor of Philosophy

Department

Chemical Physics

First Advisor

Dr. M. Samy El-Shall

Second Advisor

Dr. James Terner

Abstract

This dissertation demonstrates the application of a vapor phase method to synthesize supported and unsupported nanoparticle catalysts for CO oxidation. The method is based on the Laser Vaporization/Controlled Condensation (LVCC) technique. The first part of this dissertation presents the vapor phase synthesis and characterization of gold nanoparticles supported on a variety of oxide supports such as CeO2, TiO2, CuO and MgO.The results indicate that Au nanoparticles supported on CeO2 exhibit higher catalytic activity than Au supported on other oxides. The high activity of the Au/CeO2 catalyst is attributed to the strong interaction of Au with CeO2. The results also indicate that 5% Au loading on CeO2 has higher activity than 2% Au or 10% Au. When comparing the catalytic activity of Au/CeO2 prepared by physical (LVCC) and chemical (deposition-precipitation)methods, it was found that the catalytic activity is higher for Au/CeO2 prepared by the deposition-precipitation method.The effect of alloying Au and Cu nanoparticles on the catalytic activity for low temperature CO oxidation was also investigated. The unsupported Au-Cu alloy nanoparticle catalyst exhibits higher catalytic activity than the activities of the individualcomponents and their physical mixtures. The XRD data of Au-Cu alloy taken after the catalysis test indicates the formation of CuO within the bimetallic nanoparticles, whichimproves the catalytic activity of Au-Cu alloy nanoparticle.The second part of this dissertation investigates the gas phase reactions of Au+ and Cu+ with CO, O2 and H2O molecules using the Laser Vaporization ionization, High-Pressure Mass Spectrometry (LVI-HPMS) technique. The gas phase reactions resulting from the interactions of Au+ with CO and O2 molecules are investigated. Although multiple additions of CO and O2 molecules on Au+ have been observed at room temperature, no evidence was found of the production of CO2. This is attributed to the presence of water molecules which effectively replace the oxygen molecules on Au+ at room temperature.Finally, the role of the metal cations Au+ and Cu+ in initiating the gas phase polymerization of butadiene and isoprene vapors was investigated.

Rights

© The Author

Is Part Of

VCU University Archives

Is Part Of

VCU Theses and Dissertations

Date of Submission

June 2008

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