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Suc Chiu Ho. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references (leaves 57-60). / Abstracts in English and Chinese. / TITLE PAGE --- p.i / THESIS COMMUTE --- p.ii / ABSTRACT (English) --- p.iii / ABSTRACT (Chinese) --- p.iv / ACKNOWLEDGMENTS --- p.v / TABLE OF CONTENTS --- p.vi / LIST OF FIGURES --- p.viii / LIST OF TABLES --- p.ix / Chapter CHAPTER ONE --- General introduction and methodology / Chapter 1.1 --- General introduction --- p.1 / Chapter 1.2 --- Approximation in ab initio calculation --- p.4 / Chapter 1.2.1 --- Born-Oppenheimer approximation --- p.5 / Chapter 1.2.2 --- Density function theory (DFT) --- p.6 / Chapter 1.2.3 --- Periodic supercell approach for solid reaction --- p.8 / Chapter 1.2.4 --- Pseudopotential approximation --- p.11 / Chapter CHAPTER TWO --- "Adsorption of N02 molecules on zigzag (6,0) and (8,0) single-walled carbon nanotubes (SWNTs)" / Chapter 2.1 --- Introduction --- p.15 / Chapter 2.2 --- Computational details --- p.17 / Chapter 2.3 --- Resultsand discussion --- p.19 / Chapter 2.3.1 --- "Adsorption of a single N02 on (6,0) SWNT" --- p.19 / Chapter 2.3.2 --- "Adsorption of a second N02 on (6,0) SWNT" --- p.22 / Chapter 2.3.3 --- "Comparison of NO2 adsorptions on (8,0) SWNT with different cutoff energies" --- p.25 / Chapter 2.3.4 --- "Adsorption of more N02 on a (8,0) SWNT" --- p.28 / Chapter 2.4 --- Summary --- p.34 / Chapter CHAPTER THREE --- Diameter dependence for the adsorption of N02 molecules on zigzag single-walled carbon nanotubes (SWNTs) (n=6~12) / Chapter 3.1 --- Introduction --- p.35 / Chapter 3.2 --- Computational method --- p.37 / Chapter 3.3 --- Results and discussion --- p.38 / Chapter 3.3.1 --- Adsorption of a single N02 on SWNT --- p.38 / Chapter 3.3.2 --- Adsorption of a second on N02 SWNT --- p.40 / Chapter 3.3.3 --- Electronic structures of SWNTs after NO2 adsorption --- p.42 / Chapter 3.4 --- Summary --- p.55 / References --- p.57

acase@tulane.edu / 1 / Sijun Luo

The thesis is focused on the study of high temperature water gas shift catalysis, the identification of new improved catalysts and the study of the kinetics and mechanism of reaction over these catalysts. Rh-promoted Fe2O3-Cr2O3 was found to offer best performance which was significantly better than unpromoted catalyst over wide temperatures range. An extensive literature survey is first reported. Guidelines to develop new WGS catalysts are developed. As a result, the activities of precious metals supported on various oxides for high temperature WGS reaction have been tested. Rh(1wt%) doped Fe2O3/Cr2O3, exhibits the highest activity for WGS over a wide temperature range. 5wt%CuO/Fe2O3-Cr2O3, 1wt%Pt/Cr2O3, 1wt%Pt/Fe2O3-Cr2O3, 1wt%Pt/U3O8, 1wt%Pt/10%U3O8-Al2O3 and 1wt%Pt/5%V2O5-TiO2 fall into the second most active catalysts group, with an improved activity compared to commercial Fe2O3-Cr2O3 catalyst. It is clear that both the support/catalyst and the promoter can affect the efficiency of the WGS, leading to the obvious inference that the reaction rate is controlled at the promoter ??? support interface. Further kinetic studies and characterisation (TPR, TPD, pulse-adsorption (reaction)) on Rh/Fe3O4/Cr2O3 have been conducted. The study, conducted under conditions without inhibition from products of both forward and backward reactions, shows that the overall reaction rate expression is described as: 2 22 ??? =0.0041exp(???4042.6 ) 0.64 0.5 ???0.024 exp(???6022.9 ) 0.46 0.73 CO CO H O CO H r PP P P T T . Kinetics studies carried out under fuel reforming gas compositions shows that reaction rate expression changed when the temperature of reaction varied. The reaction rate equations at temperatures of 573K, 623K and 673K are derived as: 573K: 2 2 2 - 2.84 10-6 0.6 0.12 - 9.08 10-7 0.09 0.52 rCO = ?? PCO PH O ?? PCO PH 623K: 2 2 2 - 1.45 10-6 0.99 0.40 - 7.12 10-7 0.11 0.73 rCO = ?? PCO PH O ?? PCO PH 673K: -6 2 2 2 - = 4.37 ?? 10 0.86 0.41 -1.83 ??10-6 0.28 0.66 rCO PCO PH O PCO PH , The apparent activation energy was 61.7??2.5 kJmol-1 . TPR, TPD, TPO characterisation studies and reoxidation of catalysts by CO2 or H2O show that the active site for high temperature WGS reaction on Rh/Fe2O3/Cr2O3 is reduced magnetite Fe3O4 which dissociatively breaks down the H2O to form H* and OH* and adsorbs CO2. The deposited metal, Rh, acts as a promoter by facilitating the uptake of hydrogen (H2) and carbon monoxide (CO), desorption of H2 (at high temperature) and CO2.

Transition metal oxides exhibit potential in various application fields due to the special d-electrons. Solid state chemistry focuses on discovering the structure-property relationships. The work in this thesis mainly discusses compounds with hexagonal or brownmillerite-type structure and their practical properties. Hexagonal YIn[subscript 1-x]Fe[subscript x]O��� (x = 0-0.3, 0.7-1.0) phases have been prepared and characterized. All phases appear to have the ferroelectric structure known for YInO���. The color of the phases changes from yellow to orange to dark red with increasing Fe content. Magnetic measurements confirm high-spin Fe����� for all phases. Similarly, solid solution YAl[subscript 1-x]Fe[subscript x]O��� (x = 0-0.4, 0.7-1.0) phases were successfully synthesized through the sol-gel method. The Al-rich compounds present paraelectric YAlO��� structure while the Fe-rich side samples exhibit YFeO��� structure. The color of the compounds appear to be yellow with small Fe content and change to brown which has higher Fe content. Brownmillerite-type oxides Ba���In[subscript 2-x]Mn[subscript x]O[subscript 5+x] (x = 0.1-0.7) have been prepared and characterized. Magnetic measurements confirm that Mn in as prepared samples is substituting as Mn������ for all values of x with observed paramagnetic spin-only moments close to values expected for two unpaired electrons. Neutron diffraction structure refinements show Mn������ occupies tetrahedral sites for orthorhombic (x = 0.1) and tetragonal (x = 0.2) phases. For Mn ��� 0.3 samples, neutron refinements show the phases are cubic with disordered cations and oxygen vacancies. The colors of the phases change from light yellow (x = 0) to intense turquoise (x =0.1), to green (x = 0.2, 0.3) or dark green (x ��� 0.4). Solid solution Ba���In[subscript 2-x]Fe[subscript x]O[subscript 5+y] (x = 0.1-1.5) also exhibit brownmillerite-type structure. The color of the compounds appear to be green with small Fe content and change to black with higher Fe content (x ��� 0.3). Magnetic measurements and M��ssbauer spectroscopy conclude the mixed valence of Fe�����/Fe������ for all the phases. Nonstoichiometry compound YCu���.���Ti���.���O[subscript 3-��] has been prepared and characterized. Structure study indicates that oxygen vacancy is favored under the synthesis condition. This change in oxygen content was further studied in the Mn-doped system. And the effect of stoichiometric difference in the Mn-doped samples was not as obvious as the initial compound. The disorder in the cation site enhanced the tolerance of the structure in the aspect of oxygen content. The hexagonal phases LnCu���.���Ti���.���O��� (Ln = Y, Tb-Lu) phases were prepared by the traditional solid state reactions. The prepared compounds were reduced at high temperature in the reduction atmosphere created by the H���/N��� gas mixture. Study on the structure and properties changes by reduction was conducted by X-ray diffraction, optical measurement, magnetic measurement and thermalgravimetric analysis. And we observed some evidence of the presence of Cu��� in the reduced phase by these characterization methods. Solid solution YMn[subscript x]Ti[subscript y]O[subscript 3-��] (y = 0.1-0.4) was successfully prepared through conventional solid state approach. All the samples showed hexagonal structure. But the structure transition from ferroelectric P6���cm to paraelectric P6���/mmc occurred when Ti amount is higher than 0.2. Based on the neutron diffraction refinement, the lattice expanded in the ab plane but contracted along the c axis direction. / Graduation date: 2013

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Thesis (Ph. D.)--Lehigh University, 2002. / Includes vita. Includes bibliographical references (leaves 94-97).

Thesis (Ph. D.)--University of Texas at Austin, 2002. / Vita. Includes bibliographical references. Available also from UMI Company.

Thesis (Ph. D.)--Drexel University, 2004. / Includes abstract and vita. Includes bibliographical references (leaves 180-192).

Thesis (M.S. in E.A.S.)--School of Earth and Atmospheric Sciences, Georgia Institute of Technology, 2004. Directed by Martial Taillefert. / Includes bibliographical references (leaves 72-79).