Thesis (Ph.D.)--University of Wyoming, 2007. / Title from PDF title page (viewed on June 22, 2009). Includes bibliographical references.

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With the dwindling availability of petroleum, focus has shifted to renewable energy sources such as lignocellulosic biomass. Cellulose and hemicellulose are highly utilized components of biomass, and on the other hand, lignin is a plentiful, under-utilized component of the lignocellulosic biomass. Hence, utilization of the lignin component is necessary for the realization of an economically sustainable biorefinery model. Once depolymerized, lignin has the potential to replace petroleum-derived molecules. Further, a catalyst is capable of selectively removing the oxygen atoms without hydrogenating the aromatic components would be valuable. Bimetallic phosphides and zeolites are capable of selectively cleaving CAROMATIC–O bonds from aromatic compounds. In the present study, the applications of a bimetallic phosphides (FeMoP, RuMoP and NiMoP) for CAROMATIC–O bond cleavage and hydrogenation of C=O and C=C bond in the aromatic model compounds (Phenol, furfural, cinnamaldehyde, and CO2) were examined. The Fe:Mo ratio was varied in FeX Mo2−X P catalysts (0.88 to 1.55) to investigate the effect of catalyst acidity and hydrogenolysis capability via first principle calculations. The most acidic material was most selective for phenol to benzene. Further, combination of different transition metals with phosphorus were tested for hydrogenolysis and hydrogenation mechanism of phenol. Additionally, composition effect in RuXMo2−XP (X = 0.8, 1.0 and 1.2) have investigated for furfural and cinnamaldehyde hydrogenation. It was found that tuning in metal combination and composition results in control of binding energy and activation energy barrier which tune the selectivity for desire reaction and reaction pathway. Alternatively, highly active MWW-zeolite nanosheets have recently been explored for depolymerization in lignin. First, binding strength of different lignin dimers (phenolic and non-phenolic) was studied in terms of binding energy and binding mode over different terminated zeolite surface as a function of temperature and solvent. The optimized binding structure of lignin dimers were further considered to study the hydrogenolysis pathways over Al- and Sn-substituted MWW zeolite nanosheets. Generally, it was found that fully hydroxyl terminated surface, phenolic dimers and higher temperature in methanol pro- motes higher binding energy. Moreover, Al-substituted zeolite nanosheet resulted in lowering activation energy barriers significantly to cleave β-O-4 Linkages in Lignin dimers.

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This study highlights the importance of the anion in the electrochemical uptake of lithium by metal phosphides. It is shown through a variety of <em>in-situ</em> and <em>ex-situ</em> analytical techniques that the redox active centers in three different systems (MnP<i>₄</i>, FeP<i>₂</i>, and CoP<i>₃</i>) are not necessarily cationic but can rest almost entirely upon the anionic network, thanks to the high degree of covalency of the metal-phosphorus bond and strong P-character of the uppermost filled electronic bands in the phosphides. The electrochemical mechanism responsible for reversible Li uptake depends on the transition metal, whether a lithiated ternary phase exists in the phase diagram with the same M:P stoichiometry as the binary phase, and on the structure of the starting phase. When both binary and lithiated ternary phases of the transition metal exist, as in the case of MnP<i>₄</i> and Li<i>₇</i>MnP<i>₄</i>, a semi-topotactic phase transformation between binary and ternary phases occurs upon lithium uptake and removal. When only the binary phase exists two different behaviours are observed. In the FeP<i>₂</i> system, lithium uptake leads to the formation of an amorphous material in which short-range order persists; removal of lithium reforms some the long-range order bonds. In the case of CoP<i>₃</i>, lithium uptake results in phase decomposition to metallic cobalt plus lithium triphosphide, which becomes the active material for the subsequent cycles.

This study highlights the importance of the anion in the electrochemical uptake of lithium by metal phosphides. It is shown through a variety of <em>in-situ</em> and <em>ex-situ</em> analytical techniques that the redox active centers in three different systems (MnP<i>₄</i>, FeP<i>₂</i>, and CoP<i>₃</i>) are not necessarily cationic but can rest almost entirely upon the anionic network, thanks to the high degree of covalency of the metal-phosphorus bond and strong P-character of the uppermost filled electronic bands in the phosphides. The electrochemical mechanism responsible for reversible Li uptake depends on the transition metal, whether a lithiated ternary phase exists in the phase diagram with the same M:P stoichiometry as the binary phase, and on the structure of the starting phase. When both binary and lithiated ternary phases of the transition metal exist, as in the case of MnP<i>₄</i> and Li<i>₇</i>MnP<i>₄</i>, a semi-topotactic phase transformation between binary and ternary phases occurs upon lithium uptake and removal. When only the binary phase exists two different behaviours are observed. In the FeP<i>₂</i> system, lithium uptake leads to the formation of an amorphous material in which short-range order persists; removal of lithium reforms some the long-range order bonds. In the case of CoP<i>₃</i>, lithium uptake results in phase decomposition to metallic cobalt plus lithium triphosphide, which becomes the active material for the subsequent cycles.

We present study of the synthesis and reactions of an analog of the meteoritic mineral schreibersite with formula (Fe,Ni)3P, believed to be a prebiotic source of reactive phosphorus that may have prompted the formation of phosphorylated biomolecules near the time of the origin of life (Pasek and Lauretta, 2005). The mineral was synthesized by mixing stoichiometric proportions of elemental iron, nickel and phosphorus and heating in a tube furnace at 820°C for approximately 235 hours under argon or under vacuum, a modification of the method of Skála and Drábek (2002). The mineral was characterized using X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), micro-raman spectroscopy and electron microprobe analysis (EMPA). Characterization indicates that both schreibersite, with approximate formula Fe2NiP and the mineral nickel-phosphide, FeNi2P were synthesized. In addition to characterization of the solid product, the reactions of the synthetic schreibersite were investigated to determine the similarity between these and prior work done with Fe3P. Synthetic schreibersite was corroded in several solutions: seawater and sulfidic water under both oxic and anoxic conditions. After corrosion, the solutions were analyzed using phosphorus nuclear magnetic resonance spectroscopy (31P NMR) and high performance liquid chromatography attached to an inductively coupled plasma mass spectrometer (HPLC-ICP-MS) to determine phosphorus speciation as well as concentrations of phosphorus present in solution. As expected from previous studies, the NMR and HPLC-ICP-MS results indicated the presence of orthophosphate, phosphite, pyrophosphate and hypophosphate in the corrosion solutions (Pasek and Lauretta, 2005). The HPLC-ICP-MS results indicate that the extent of corrosion of the mineral—measured by the concentration of phosphorus released—depends on the ionic strength of the solution, as well as the presence or absence of the chelating agent. Finally, we report the successful phosphorylation of a potentially prebiotic molecule—choline—using synthesized schreibersite.

Thesis (M.S.)--Ohio University, August, 2000. / Title from PDF t.p.